Module 15: The Cardiovascular System: Blood Vessels and Circulation

Lesson 4: Homeostatic Regulation of the Vascular System

Điều Hòa Cân Bằng Nội Môi Hệ Mạch Máu

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Dưới đây là danh sách những thuật ngữ Y khoa của module The Cardiovascular System: Blood Vessels and Circulation.
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Medical Terminology: The Cardiovascular System: Blood Vessels and Circulation

abdominal aorta
portion of the aorta inferior to the aortic hiatus and superior to the common iliac arteries
adrenal artery
branch of the abdominal aorta; supplies blood to the adrenal (suprarenal) glands
adrenal vein
drains the adrenal or suprarenal glands that are immediately superior to the kidneys; the right adrenal vein enters the inferior vena cava directly and the left adrenal vein enters the left renal vein
anaphylactic shock
type of shock that follows a severe allergic reaction and results from massive vasodilation
angioblasts
stem cells that give rise to blood vessels
angiogenesis
development of new blood vessels from existing vessels
anterior cerebral artery
arises from the internal carotid artery; supplies the frontal lobe of the cerebrum
anterior communicating artery
anastomosis of the right and left internal carotid arteries; supplies blood to the brain
anterior tibial artery
branches from the popliteal artery; supplies blood to the anterior tibial region; becomes the dorsalis pedis artery
anterior tibial vein
forms from the dorsal venous arch; drains the area near the tibialis anterior muscle and leads to the popliteal vein
aorta
largest artery in the body, originating from the left ventricle and descending to the abdominal region where it bifurcates into the common iliac arteries at the level of the fourth lumbar vertebra; arteries originating from the aorta distribute blood to virtually all tissues of the body
aortic arch
arc that connects the ascending aorta to the descending aorta; ends at the intervertebral disk between the fourth and fifth thoracic vertebrae
aortic hiatus
opening in the diaphragm that allows passage of the thoracic aorta into the abdominal region where it becomes the abdominal aorta
aortic sinuses
small pockets in the ascending aorta near the aortic valve that are the locations of the baroreceptors (stretch receptors) and chemoreceptors that trigger a reflex that aids in the regulation of vascular homeostasis
arterial circle
(also, circle of Willis) anastomosis located at the base of the brain that ensures continual blood supply; formed from branches of the internal carotid and vertebral arteries; supplies blood to the brain
arteriole
(also, resistance vessel) very small artery that leads to a capillary
arteriovenous anastomosis
short vessel connecting an arteriole directly to a venule and bypassing the capillary beds
artery
blood vessel that conducts blood away from the heart; may be a conducting or distributing vessel
ascending aorta
initial portion of the aorta, rising from the left ventricle for a distance of approximately 5 cm
atrial reflex
mechanism for maintaining vascular homeostasis involving atrial baroreceptors: if blood is returning to the right atrium more rapidly than it is being ejected from the left ventricle, the atrial receptors will stimulate the cardiovascular centers to increase sympathetic firing and increase cardiac output until the situation is reversed; the opposite is also true
axillary artery
continuation of the subclavian artery as it penetrates the body wall and enters the axillary region; supplies blood to the region near the head of the humerus (humeral circumflex arteries); the majority of the vessel continues into the brachium and becomes the brachial artery
axillary vein
major vein in the axillary region; drains the upper limb and becomes the subclavian vein
azygos vein
originates in the lumbar region and passes through the diaphragm into the thoracic cavity on the right side of the vertebral column; drains blood from the intercostal veins, esophageal veins, bronchial veins, and other veins draining the mediastinal region; leads to the superior vena cava
basilar artery
formed from the fusion of the two vertebral arteries; sends branches to the cerebellum, brain stem, and the posterior cerebral arteries; the main blood supply to the brain stem
basilic vein
superficial vein of the arm that arises from the palmar venous arches, intersects with the median cubital vein, parallels the ulnar vein, and continues into the upper arm; along with the brachial vein, it leads to the axillary vein
blood colloidal osmotic pressure (BCOP)
pressure exerted by colloids suspended in blood within a vessel; a primary determinant is the presence of plasma proteins
blood flow
movement of blood through a vessel, tissue, or organ that is usually expressed in terms of volume per unit of time
blood hydrostatic pressure
force blood exerts against the walls of a blood vessel or heart chamber
blood islands
masses of developing blood vessels and formed elements from mesodermal cells scattered throughout the embryonic disc
blood pressure
force exerted by the blood against the wall of a vessel or heart chamber; can be described with the more generic term hydrostatic pressure
brachial artery
continuation of the axillary artery in the brachium; supplies blood to much of the brachial region; gives off several smaller branches that provide blood to the posterior surface of the arm in the region of the elbow; bifurcates into the radial and ulnar arteries at the coronoid fossa
brachial vein
deeper vein of the arm that forms from the radial and ulnar veins in the lower arm; leads to the axillary vein
brachiocephalic artery
single vessel located on the right side of the body; the first vessel branching from the aortic arch; gives rise to the right subclavian artery and the right common carotid artery; supplies blood to the head, neck, upper limb, and wall of the thoracic region
brachiocephalic vein
one of a pair of veins that form from a fusion of the external and internal jugular veins and the subclavian vein; subclavian, external and internal jugulars, vertebral, and internal thoracic veins lead to it; drains the upper thoracic region and flows into the superior vena cava
bronchial artery
systemic branch from the aorta that provides oxygenated blood to the lungs in addition to the pulmonary circuit
bronchial vein
drains the systemic circulation from the lungs and leads to the azygos vein
capacitance
ability of a vein to distend and store blood
capacitance vessels
veins
capillary
smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid
capillary bed
network of 10–100 capillaries connecting arterioles to venules
capillary hydrostatic pressure (CHP)
force blood exerts against a capillary
cardiogenic shock
type of shock that results from the inability of the heart to maintain cardiac output
carotid sinuses
small pockets near the base of the internal carotid arteries that are the locations of the baroreceptors and chemoreceptors that trigger a reflex that aids in the regulation of vascular homeostasis
cavernous sinus
enlarged vein that receives blood from most of the other cerebral veins and the eye socket, and leads to the petrosal sinus
celiac trunk
(also, celiac artery) major branch of the abdominal aorta; gives rise to the left gastric artery, the splenic artery, and the common hepatic artery that forms the hepatic artery to the liver, the right gastric artery to the stomach, and the cystic artery to the gall bladder
cephalic vein
superficial vessel in the upper arm; leads to the axillary vein
cerebrovascular accident (CVA)
blockage of blood flow to the brain; also called a stroke
circle of Willis
(also, arterial circle) anastomosis located at the base of the brain that ensures continual blood supply; formed from branches of the internal carotid and vertebral arteries; supplies blood to the brain
circulatory shock
also simply called shock; a life-threatening medical condition in which the circulatory system is unable to supply enough blood flow to provide adequate oxygen and other nutrients to the tissues to maintain cellular metabolism
common carotid artery
right common carotid artery arises from the brachiocephalic artery, and the left common carotid arises from the aortic arch; gives rise to the external and internal carotid arteries; supplies the respective sides of the head and neck
common hepatic artery
branch of the celiac trunk that forms the hepatic artery, the right gastric artery, and the cystic artery
common iliac artery
branch of the aorta that leads to the internal and external iliac arteries
common iliac vein
one of a pair of veins that flows into the inferior vena cava at the level of L5; the left common iliac vein drains the sacral region; divides into external and internal iliac veins near the inferior portion of the sacroiliac joint
compliance
degree to which a blood vessel can stretch as opposed to being rigid
continuous capillary
most common type of capillary, found in virtually all tissues except epithelia and cartilage; contains very small gaps in the endothelial lining that permit exchange
cystic artery
branch of the common hepatic artery; supplies blood to the gall bladder
deep femoral artery
branch of the femoral artery; gives rise to the lateral circumflex arteries
deep femoral vein
drains blood from the deeper portions of the thigh and leads to the femoral vein
descending aorta
portion of the aorta that continues downward past the end of the aortic arch; subdivided into the thoracic aorta and the abdominal aorta
diastolic pressure
lower number recorded when measuring arterial blood pressure; represents the minimal value corresponding to the pressure that remains during ventricular relaxation
digital arteries
formed from the superficial and deep palmar arches; supply blood to the digits
digital veins
drain the digits and feed into the palmar arches of the hand and dorsal venous arch of the foot
dorsal arch
(also, arcuate arch) formed from the anastomosis of the dorsalis pedis artery and medial and plantar arteries; branches supply the distal portions of the foot and digits
dorsal venous arch
drains blood from digital veins and vessels on the superior surface of the foot
dorsalis pedis artery
forms from the anterior tibial artery; branches repeatedly to supply blood to the tarsal and dorsal regions of the foot
ductus arteriosus
shunt in the fetal pulmonary trunk that diverts oxygenated blood back to the aorta
ductus venosus
shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava
elastic artery
(also, conducting artery) artery with abundant elastic fibers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches
esophageal artery
branch of the thoracic aorta; supplies blood to the esophagus
esophageal vein
drains the inferior portions of the esophagus and leads to the azygos vein
external carotid artery
arises from the common carotid artery; supplies blood to numerous structures within the face, lower jaw, neck, esophagus, and larynx
external elastic membrane
membrane composed of elastic fibers that separates the tunica media from the tunica externa; seen in larger arteries
external iliac artery
branch of the common iliac artery that leaves the body cavity and becomes a femoral artery; supplies blood to the lower limbs
external iliac vein
formed when the femoral vein passes into the body cavity; drains the legs and leads to the common iliac vein
external jugular vein
one of a pair of major veins located in the superficial neck region that drains blood from the more superficial portions of the head, scalp, and cranial regions, and leads to the subclavian vein
femoral artery
continuation of the external iliac artery after it passes through the body cavity; divides into several smaller branches, the lateral deep femoral artery, and the genicular artery; becomes the popliteal artery as it passes posterior to the knee
femoral circumflex vein
forms a loop around the femur just inferior to the trochanters; drains blood from the areas around the head and neck of the femur; leads to the femoral vein
femoral vein
drains the upper leg; receives blood from the great saphenous vein, the deep femoral vein, and the femoral circumflex vein; becomes the external iliac vein when it crosses the body wall
fenestrated capillary
type of capillary with pores or fenestrations in the endothelium that allow for rapid passage of certain small materials
fibular vein
drains the muscles and integument near the fibula and leads to the popliteal vein
filtration
in the cardiovascular system, the movement of material from a capillary into the interstitial fluid, moving from an area of higher pressure to lower pressure
foramen ovale
shunt that directly connects the right and left atria and helps to divert oxygenated blood from the fetal pulmonary circuit
genicular artery
branch of the femoral artery; supplies blood to the region of the knee
gonadal artery
branch of the abdominal aorta; supplies blood to the gonads or reproductive organs; also described as ovarian arteries or testicular arteries, depending upon the sex of the individual
gonadal vein
generic term for a vein draining a reproductive organ; may be either an ovarian vein or a testicular vein, depending on the sex of the individual
great cerebral vein
receives most of the smaller vessels from the inferior cerebral veins and leads to the straight sinus
great saphenous vein
prominent surface vessel located on the medial surface of the leg and thigh; drains the superficial portions of these areas and leads to the femoral vein
hemangioblasts
embryonic stem cells that appear in the mesoderm and give rise to both angioblasts and pluripotent stem cells
hemiazygos vein
smaller vein complementary to the azygos vein; drains the esophageal veins from the esophagus and the left intercostal veins, and leads to the brachiocephalic vein via the superior intercostal vein
hepatic artery proper
branch of the common hepatic artery; supplies systemic blood to the liver
hepatic portal system
specialized circulatory pathway that carries blood from digestive organs to the liver for processing before being sent to the systemic circulation
hepatic vein
drains systemic blood from the liver and flows into the inferior vena cava
hypertension
chronic and persistent blood pressure measurements of 140/90 mm Hg or above
hypervolemia
abnormally high levels of fluid and blood within the body
hypovolemia
abnormally low levels of fluid and blood within the body
hypovolemic shock
type of circulatory shock caused by excessive loss of blood volume due to hemorrhage or possibly dehydration
hypoxia
lack of oxygen supply to the tissues
inferior mesenteric artery
branch of the abdominal aorta; supplies blood to the distal segment of the large intestine and rectum
inferior phrenic artery
branch of the abdominal aorta; supplies blood to the inferior surface of the diaphragm
inferior vena cava
large systemic vein that drains blood from areas largely inferior to the diaphragm; empties into the right atrium
intercostal artery
branch of the thoracic aorta; supplies blood to the muscles of the thoracic cavity and vertebral column
intercostal vein
drains the muscles of the thoracic wall and leads to the azygos vein
internal carotid artery
arises from the common carotid artery and begins with the carotid sinus; goes through the carotid canal of the temporal bone to the base of the brain; combines with branches of the vertebral artery forming the arterial circle; supplies blood to the brain
internal elastic membrane
membrane composed of elastic fibers that separates the tunica intima from the tunica media; seen in larger arteries
internal iliac artery
branch from the common iliac arteries; supplies blood to the urinary bladder, walls of the pelvis, external genitalia, and the medial portion of the femoral region; in females, also provide blood to the uterus and vagina
internal iliac vein
drains the pelvic organs and integument; formed from several smaller veins in the region; leads to the common iliac vein
internal jugular vein
one of a pair of major veins located in the neck region that passes through the jugular foramen and canal, flows parallel to the common carotid artery that is more or less its counterpart; primarily drains blood from the brain, receives the superficial facial vein, and empties into the subclavian vein
internal thoracic artery
(also, mammary artery) arises from the subclavian artery; supplies blood to the thymus, pericardium of the heart, and the anterior chest wall
internal thoracic vein
(also, internal mammary vein) drains the anterior surface of the chest wall and leads to the brachiocephalic vein
interstitial fluid colloidal osmotic pressure (IFCOP)
pressure exerted by the colloids within the interstitial fluid
interstitial fluid hydrostatic pressure (IFHP)
force exerted by the fluid in the tissue spaces
ischemia
insufficient blood flow to the tissues
Korotkoff sounds
noises created by turbulent blood flow through the vessels
lateral circumflex artery
branch of the deep femoral artery; supplies blood to the deep muscles of the thigh and the ventral and lateral regions of the integument
lateral plantar artery
arises from the bifurcation of the posterior tibial arteries; supplies blood to the lateral plantar surfaces of the foot
left gastric artery
branch of the celiac trunk; supplies blood to the stomach
lumbar arteries
branches of the abdominal aorta; supply blood to the lumbar region, the abdominal wall, and spinal cord
lumbar veins
drain the lumbar portion of the abdominal wall and spinal cord; the superior lumbar veins drain into the azygos vein on the right or the hemiazygos vein on the left; blood from these vessels is returned to the superior vena cava rather than the inferior vena cava
lumen
interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel
maxillary vein
drains blood from the maxillary region and leads to the external jugular vein
mean arterial pressure (MAP)
average driving force of blood to the tissues; approximated by taking diastolic pressure and adding 1/3 of pulse pressure
medial plantar artery
arises from the bifurcation of the posterior tibial arteries; supplies blood to the medial plantar surfaces of the foot
median antebrachial vein
vein that parallels the ulnar vein but is more medial in location; intertwines with the palmar venous arches
median cubital vein
superficial vessel located in the antecubital region that links the cephalic vein to the basilic vein in the form of a v; a frequent site for a blood draw
median sacral artery
continuation of the aorta into the sacrum
mediastinal artery
branch of the thoracic aorta; supplies blood to the mediastinum
metarteriole
short vessel arising from a terminal arteriole that branches to supply a capillary bed
microcirculation
blood flow through the capillaries
middle cerebral artery
another branch of the internal carotid artery; supplies blood to the temporal and parietal lobes of the cerebrum
middle sacral vein
drains the sacral region and leads to the left common iliac vein
muscular artery
(also, distributing artery) artery with abundant smooth muscle in the tunica media that branches to distribute blood to the arteriole network
myogenic response
constriction or dilation in the walls of arterioles in response to pressures related to blood flow; reduces high blood flow or increases low blood flow to help maintain consistent flow to the capillary network
nervi vasorum
small nerve fibers found in arteries and veins that trigger contraction of the smooth muscle in their walls
net filtration pressure (NFP)
force driving fluid out of the capillary and into the tissue spaces; equal to the difference of the capillary hydrostatic pressure and the blood colloidal osmotic pressure
neurogenic shock
type of shock that occurs with cranial or high spinal injuries that damage the cardiovascular centers in the medulla oblongata or the nervous fibers originating from this region
obstructive shock
type of shock that occurs when a significant portion of the vascular system is blocked
occipital sinus
enlarged vein that drains the occipital region near the falx cerebelli and flows into the left and right transverse sinuses, and also into the vertebral veins
ophthalmic artery
branch of the internal carotid artery; supplies blood to the eyes
ovarian artery
branch of the abdominal aorta; supplies blood to the ovary, uterine (Fallopian) tube, and uterus
ovarian vein
drains the ovary; the right ovarian vein leads to the inferior vena cava and the left ovarian vein leads to the left renal vein
palmar arches
superficial and deep arches formed from anastomoses of the radial and ulnar arteries; supply blood to the hand and digital arteries
palmar venous arches
drain the hand and digits, and feed into the radial and ulnar veins
parietal branches
(also, somatic branches) group of arterial branches of the thoracic aorta; includes those that supply blood to the thoracic cavity, vertebral column, and the superior surface of the diaphragm
perfusion
distribution of blood into the capillaries so the tissues can be supplied
pericardial artery
branch of the thoracic aorta; supplies blood to the pericardium
petrosal sinus
enlarged vein that receives blood from the cavernous sinus and flows into the internal jugular vein
phrenic vein
drains the diaphragm; the right phrenic vein flows into the inferior vena cava and the left phrenic vein leads to the left renal vein
plantar arch
formed from the anastomosis of the dorsalis pedis artery and medial and plantar arteries; branches supply the distal portions of the foot and digits
plantar veins
drain the foot and lead to the plantar venous arch
plantar venous arch
formed from the plantar veins; leads to the anterior and posterior tibial veins through anastomoses
popliteal artery
continuation of the femoral artery posterior to the knee; branches into the anterior and posterior tibial arteries
popliteal vein
continuation of the femoral vein behind the knee; drains the region behind the knee and forms from the fusion of the fibular and anterior and posterior tibial veins
posterior cerebral artery
branch of the basilar artery that forms a portion of the posterior segment of the arterial circle; supplies blood to the posterior portion of the cerebrum and brain stem
posterior communicating artery
branch of the posterior cerebral artery that forms part of the posterior portion of the arterial circle; supplies blood to the brain
posterior tibial artery
branch from the popliteal artery that gives rise to the fibular or peroneal artery; supplies blood to the posterior tibial region
posterior tibial vein
forms from the dorsal venous arch; drains the area near the posterior surface of the tibia and leads to the popliteal vein
precapillary sphincters
circular rings of smooth muscle that surround the entrance to a capillary and regulate blood flow into that capillary
pulmonary artery
one of two branches, left and right, that divides off from the pulmonary trunk and leads to smaller arterioles and eventually to the pulmonary capillaries
pulmonary circuit
system of blood vessels that provide gas exchange via a network of arteries, veins, and capillaries that run from the heart, through the body, and back to the lungs
pulmonary trunk
single large vessel exiting the right ventricle that divides to form the right and left pulmonary arteries
pulmonary veins
two sets of paired vessels, one pair on each side, that are formed from the small venules leading away from the pulmonary capillaries that flow into the left atrium
pulse
alternating expansion and recoil of an artery as blood moves through the vessel; an indicator of heart rate
pulse pressure
difference between the systolic and diastolic pressures
radial artery
formed at the bifurcation of the brachial artery; parallels the radius; gives off smaller branches until it reaches the carpal region where it fuses with the ulnar artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
radial vein
parallels the radius and radial artery; arises from the palmar venous arches and leads to the brachial vein
reabsorption
in the cardiovascular system, the movement of material from the interstitial fluid into the capillaries
renal artery
branch of the abdominal aorta; supplies each kidney
renal vein
largest vein entering the inferior vena cava; drains the kidneys and leads to the inferior vena cava
resistance
any condition or parameter that slows or counteracts the flow of blood
respiratory pump
increase in the volume of the thorax during inhalation that decreases air pressure, enabling venous blood to flow into the thoracic region, then exhalation increases pressure, moving blood into the atria
right gastric artery
branch of the common hepatic artery; supplies blood to the stomach
sepsis
(also, septicemia) organismal-level inflammatory response to a massive infection
septic shock
(also, blood poisoning) type of shock that follows a massive infection resulting in organism-wide inflammation
sigmoid sinuses
enlarged veins that receive blood from the transverse sinuses; flow through the jugular foramen and into the internal jugular vein
sinusoid capillary
rarest type of capillary, which has extremely large intercellular gaps in the basement membrane in addition to clefts and fenestrations; found in areas such as the bone marrow and liver where passage of large molecules occurs
skeletal muscle pump
effect on increasing blood pressure within veins by compression of the vessel caused by the contraction of nearby skeletal muscle
small saphenous vein
located on the lateral surface of the leg; drains blood from the superficial regions of the lower leg and foot, and leads to the popliteal vein
sphygmomanometer
blood pressure cuff attached to a device that measures blood pressure
splenic artery
branch of the celiac trunk; supplies blood to the spleen
straight sinus
enlarged vein that drains blood from the brain; receives most of the blood from the great cerebral vein and flows into the left or right transverse sinus
subclavian artery
right subclavian arises from the brachiocephalic artery, whereas the left subclavian artery arises from the aortic arch; gives rise to the internal thoracic, vertebral, and thyrocervical arteries; supplies blood to the arms, chest, shoulders, back, and central nervous system
subclavian vein
located deep in the thoracic cavity; becomes the axillary vein as it enters the axillary region; drains the axillary and smaller local veins near the scapular region; leads to the brachiocephalic vein
subscapular vein
drains blood from the subscapular region and leads to the axillary vein
superior mesenteric artery
branch of the abdominal aorta; supplies blood to the small intestine (duodenum, jejunum, and ileum), the pancreas, and a majority of the large intestine
superior phrenic artery
branch of the thoracic aorta; supplies blood to the superior surface of the diaphragm
superior sagittal sinus
enlarged vein located midsagittally between the meningeal and periosteal layers of the dura mater within the falx cerebri; receives most of the blood drained from the superior surface of the cerebrum and leads to the inferior jugular vein and the vertebral vein
superior vena cava
large systemic vein; drains blood from most areas superior to the diaphragm; empties into the right atrium
systolic pressure
larger number recorded when measuring arterial blood pressure; represents the maximum value following ventricular contraction
temporal vein
drains blood from the temporal region and leads to the external jugular vein
testicular artery
branch of the abdominal aorta; will ultimately travel outside the body cavity to the testes and form one component of the spermatic cord
testicular vein
drains the testes and forms part of the spermatic cord; the right testicular vein empties directly into the inferior vena cava and the left testicular vein empties into the left renal vein
thoracic aorta
portion of the descending aorta superior to the aortic hiatus
thoroughfare channel
continuation of the metarteriole that enables blood to bypass a capillary bed and flow directly into a venule, creating a vascular shunt
thyrocervical artery
arises from the subclavian artery; supplies blood to the thyroid, the cervical region, the upper back, and shoulder
transient ischemic attack (TIA)
temporary loss of neurological function caused by a brief interruption in blood flow; also known as a mini-stroke
transverse sinuses
pair of enlarged veins near the lambdoid suture that drain the occipital, sagittal, and straight sinuses, and leads to the sigmoid sinuses
trunk
large vessel that gives rise to smaller vessels
tunica externa
(also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)
tunica intima
(also, tunica interna) innermost lining or tunic of a vessel
tunica media
middle layer or tunic of a vessel (except capillaries)
ulnar artery
formed at the bifurcation of the brachial artery; parallels the ulna; gives off smaller branches until it reaches the carpal region where it fuses with the radial artery to form the superficial and deep palmar arches; supplies blood to the lower arm and carpal region
ulnar vein
parallels the ulna and ulnar artery; arises from the palmar venous arches and leads to the brachial vein
umbilical arteries
pair of vessels that runs within the umbilical cord and carries fetal blood low in oxygen and high in waste to the placenta for exchange with maternal blood
umbilical vein
single vessel that originates in the placenta and runs within the umbilical cord, carrying oxygen- and nutrient-rich blood to the fetal heart
vasa vasorum
small blood vessels located within the walls or tunics of larger vessels that supply nourishment to and remove wastes from the cells of the vessels
vascular shock
type of shock that occurs when arterioles lose their normal muscular tone and dilate dramatically
vascular shunt
continuation of the metarteriole and thoroughfare channel that allows blood to bypass the capillary beds to flow directly from the arterial to the venous circulation
vascular tone
contractile state of smooth muscle in a blood vessel
vascular tubes
rudimentary blood vessels in a developing fetus
vasoconstriction
constriction of the smooth muscle of a blood vessel, resulting in a decreased vascular diameter
vasodilation
relaxation of the smooth muscle in the wall of a blood vessel, resulting in an increased vascular diameter
vasomotion
irregular, pulsating flow of blood through capillaries and related structures
vein
blood vessel that conducts blood toward the heart
venous reserve
volume of blood contained within systemic veins in the integument, bone marrow, and liver that can be returned to the heart for circulation, if needed
venule
small vessel leading from the capillaries to veins
vertebral artery
arises from the subclavian artery and passes through the vertebral foramen through the foramen magnum to the brain; joins with the internal carotid artery to form the arterial circle; supplies blood to the brain and spinal cord
vertebral vein
arises from the base of the brain and the cervical region of the spinal cord; passes through the intervertebral foramina in the cervical vertebrae; drains smaller veins from the cranium, spinal cord, and vertebrae, and leads to the brachiocephalic vein; counterpart of the vertebral artery
visceral branches
branches of the descending aorta that supply blood to the viscera
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In order to maintain homeostasis in the cardiovascular system and provide adequate blood to the tissues, blood flow must be redirected continually to the tissues as they become more active. In a very real sense, the cardiovascular system engages in resource allocation, because there is not enough blood flow to distribute blood equally to all tissues simultaneously. For example, when an individual is exercising, more blood will be directed to skeletal muscles, the heart, and the lungs. Following a meal, more blood is directed to the digestive system. Only the brain receives a more or less constant supply of blood whether you are active, resting, thinking, or engaged in any other activity.

Table 20.3 provides the distribution of systemic blood at rest and during exercise. Although most of the data appears logical, the values for the distribution of blood to the integument may seem surprising. During exercise, the body distributes more blood to the body surface where it can dissipate the excess heat generated by increased activity into the environment.

Three homeostatic mechanisms ensure adequate blood flow, blood pressure, distribution, and ultimately perfusion: neural, endocrine, and autoregulatory mechanisms. They are summarized in Figure 1.
The nervous system plays a critical role in the regulation of vascular homeostasis. The primary regulatory sites include the cardiovascular centers in the brain that control both cardiac and vascular functions. In addition, more generalized neural responses from the limbic system and the autonomic nervous system are factors.

A. The Cardiovascular Centers in the Brain

Neurological regulation of blood pressure and flow depends on the cardiovascular centers located in the medulla oblongata. This cluster of neurons responds to changes in blood pressure as well as blood concentrations of oxygen, carbon dioxide, and hydrogen ions. The cardiovascular center contains three distinct paired components:

  • The cardioaccelerator centers stimulate cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve.
  • The cardioinhibitor centers slow cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve.
  • The vasomotor centers control vessel tone or contraction of the smooth muscle in the tunica media. Changes in diameter affect peripheral resistance, pressure, and flow, which affect cardiac output. The majority of these neurons act via the release of the neurotransmitter norepinephrine from sympathetic neurons.

Although each center functions independently, they are not anatomically distinct.

There is also a small population of neurons that control vasodilation in the vessels of the brain and skeletal muscles by relaxing the smooth muscle fibers in the vessel tunics. Many of these are cholinergic neurons, that is, they release acetylcholine, which in turn stimulates the vessels’ endothelial cells to release nitric oxide (NO), which causes vasodilation. Others release norepinephrine that binds to β2 receptors. A few neurons release NO directly as a neurotransmitter.

Recall that mild stimulation of the skeletal muscles maintains muscle tone. A similar phenomenon occurs with vascular tone in vessels. As noted earlier, arterioles are normally partially constricted: With maximal stimulation, their radius may be reduced to one-half of the resting state. Full dilation of most arterioles requires that this sympathetic stimulation be suppressed. When it is, an arteriole can expand by as much as 150 percent. Such a significant increase can dramatically affect resistance, pressure, and flow.

B. Baroreceptor Reflexes

Baroreceptors are specialized stretch receptors located within thin areas of blood vessels and heart chambers that respond to the degree of stretch caused by the presence of blood. They send impulses to the cardiovascular center to regulate blood pressure. Vascular baroreceptors are found primarily in sinuses (small cavities) within the aorta and carotid arteries: The aortic sinuses are found in the walls of the ascending aorta just superior to the aortic valve, whereas the carotid sinuses are in the base of the internal carotid arteries. There are also low-pressure baroreceptors located in the walls of the venae cavae and right atrium.

When blood pressure increases, the baroreceptors are stretched more tightly and initiate action potentials at a higher rate. At lower blood pressures, the degree of stretch is lower and the rate of firing is slower. When the cardiovascular center in the medulla oblongata receives this input, it triggers a reflex that maintains homeostasis (Figure 2):

  • When blood pressure rises too high, the baroreceptors fire at a higher rate and trigger parasympathetic stimulation of the heart. As a result, cardiac output falls. Sympathetic stimulation of the peripheral arterioles will also decrease, resulting in vasodilation. Combined, these activities cause blood pressure to fall.
  • When blood pressure drops too low, the rate of baroreceptor firing decreases. This will trigger an increase in sympathetic stimulation of the heart, causing cardiac output to increase. It will also trigger sympathetic stimulation of the peripheral vessels, resulting in vasoconstriction. Combined, these activities cause blood pressure to rise.

The baroreceptors in the venae cavae and right atrium monitor blood pressure as the blood returns to the heart from the systemic circulation. Normally, blood flow into the aorta is the same as blood flow back into the right atrium. If blood is returning to the right atrium more rapidly than it is being ejected from the left ventricle, the atrial receptors will stimulate the cardiovascular centers to increase sympathetic firing and increase cardiac output until homeostasis is achieved. The opposite is also true. This mechanism is referred to as the atrial reflex.

C. Chemoreceptor Reflexes

In addition to the baroreceptors are chemoreceptors that monitor levels of oxygen, carbon dioxide, and hydrogen ions (pH), and thereby contribute to vascular homeostasis. Chemoreceptors monitoring the blood are located in close proximity to the baroreceptors in the aortic and carotid sinuses. They signal the cardiovascular center as well as the respiratory centers in the medulla oblongata.

Since tissues consume oxygen and produce carbon dioxide and acids as waste products, when the body is more active, oxygen levels fall and carbon dioxide levels rise as cells undergo cellular respiration to meet the energy needs of activities. This causes more hydrogen ions to be produced, causing the blood pH to drop. When the body is resting, oxygen levels are higher, carbon dioxide levels are lower, more hydrogen is bound, and pH rises. (Seek additional content for more detail about pH.)

The chemoreceptors respond to increasing carbon dioxide and hydrogen ion levels (falling pH) by stimulating the cardioaccelerator and vasomotor centers, increasing cardiac output and constricting peripheral vessels. The cardioinhibitor centers are suppressed. With falling carbon dioxide and hydrogen ion levels (increasing pH), the cardioinhibitor centers are stimulated, and the cardioaccelerator and vasomotor centers are suppressed, decreasing cardiac output and causing peripheral vasodilation. In order to maintain adequate supplies of oxygen to the cells and remove waste products such as carbon dioxide, it is essential that the respiratory system respond to changing metabolic demands. In turn, the cardiovascular system will transport these gases to the lungs for exchange, again in accordance with metabolic demands. This interrelationship of cardiovascular and respiratory control cannot be overemphasized.

Other neural mechanisms can also have a significant impact on cardiovascular function. These include the limbic system that links physiological responses to psychological stimuli, as well as generalized sympathetic and parasympathetic stimulation.
Endocrine control over the cardiovascular system involves the catecholamines, epinephrine and norepinephrine, as well as several hormones that interact with the kidneys in the regulation of blood volume.

A. Epinephrine and Norepinephrine

The catecholamines epinephrine and norepinephrine are released by the adrenal medulla, and enhance and extend the body’s sympathetic or “fight-or-flight” response (see Figure 1). They increase heart rate and force of contraction, while temporarily constricting blood vessels to organs not essential for flight-or-fight responses and redirecting blood flow to the liver, muscles, and heart.

B. Antidiuretic Hormone

Antidiuretic hormone (ADH), also known as vasopressin, is secreted by the cells in the hypothalamus and transported via the hypothalamic-hypophyseal tracts to the posterior pituitary where it is stored until released upon nervous stimulation. The primary trigger prompting the hypothalamus to release ADH is increasing osmolarity of tissue fluid, usually in response to significant loss of blood volume. ADH signals its target cells in the kidneys to reabsorb more water, thus preventing the loss of additional fluid in the urine. This will increase overall fluid levels and help restore blood volume and pressure. In addition, ADH constricts peripheral vessels.

C. Renin-Angiotensin-Aldosterone Mechanism

The renin-angiotensin-aldosterone mechanism has a major effect upon the cardiovascular system (Figure 3). Renin is an enzyme, although because of its importance in the renin-angiotensin-aldosterone pathway, some sources identify it as a hormone. Specialized cells in the kidneys , called juxtaglomerular (JG) cells, respond to decreased blood pressure by secreting renin into the blood. Renin converts the plasma protein angiotensinogen, which is produced by the liver, into its active form—angiotensin I. Angiotensin I circulates in the blood and is then converted into angiotensin II in the lungs. This reaction is catalyzed by the enzyme angiotensin-converting enzyme (ACE).

Angiotensin II is a powerful vasoconstrictor, greatly increasing blood pressure. It also stimulates the release of ADH and aldosterone, a hormone produced by the adrenal cortex. Aldosterone increases the reabsorption of sodium into the blood by the kidneys. Since water follows sodium, this increases the reabsorption of water. This in turn increases blood volume, raising blood pressure. Angiotensin II also stimulates the thirst center in the hypothalamus, so an individual will likely consume more fluids, again increasing blood volume and pressure.

D. Erythropoietin

Erythropoietin (EPO) is released by the kidneys when blood flow and/or oxygen levels decrease. EPO stimulates the production of erythrocytes within the bone marrow. Erythrocytes are the major formed element of the blood and may contribute 40 percent or more to blood volume, a significant factor of viscosity, resistance, pressure, and flow. In addition, EPO is a vasoconstrictor. Overproduction of EPO or excessive intake of synthetic EPO, often to enhance athletic performance, will increase viscosity, resistance, and pressure, and decrease flow in addition to its contribution as a vasoconstrictor.

E. Atrial Natriuretic Hormone

Secreted by cells in the atria of the heart, atrial natriuretic hormone (ANH) (also known as atrial natriuretic peptide) is secreted when blood volume is high enough to cause extreme stretching of the cardiac cells. Cells in the ventricle produce a hormone with similar effects, called B-type natriuretic hormone. Natriuretic hormones are antagonists to angiotensin II. They promote loss of sodium and water from the kidneys, and suppress renin, aldosterone, and ADH production and release. All of these actions promote loss of fluid from the body, so blood volume and blood pressure drop.
As the name would suggest, autoregulation mechanisms require neither specialized nervous stimulation nor endocrine control. Rather, these are local, self-regulatory mechanisms that allow each region of tissue to adjust its blood flow—and thus its perfusion. These local mechanisms include chemical signals and myogenic controls.

A. Chemical Signals Involved in Autoregulation

Chemical signals work at the level of the precapillary sphincters to trigger either constriction or relaxation. As you know, opening a precapillary sphincter allows blood to flow into that particular capillary, whereas constricting a precapillary sphincter temporarily shuts off blood flow to that region. The factors involved in regulating the precapillary sphincters include the following:

  • Opening of the sphincter is triggered in response to decreased oxygen concentrations; increased carbon dioxide concentrations; increasing levels of lactic acid or other byproducts of cellular metabolism; increasing concentrations of potassium ions or hydrogen ions (falling pH); inflammatory chemicals such as histamines; and increased body temperature. These conditions in turn stimulate the release of NO, a powerful vasodilator, from endothelial cells (see Figure 1).
  • Contraction of the precapillary sphincter is triggered by the opposite levels of the regulators, which prompt the release of endothelins, powerful vasoconstricting peptides secreted by endothelial cells. Platelet secretions and certain prostaglandins may also trigger constriction.

Again, these factors alter tissue perfusion via their effects on the precapillary sphincter mechanism, which regulates blood flow to capillaries. Since the amount of blood is limited, not all capillaries can fill at once, so blood flow is allocated based upon the needs and metabolic state of the tissues as reflected in these parameters. Bear in mind, however, that dilation and constriction of the arterioles feeding the capillary beds is the primary control mechanism.

B. The Myogenic Response

The myogenic response is a reaction to the stretching of the smooth muscle in the walls of arterioles as changes in blood flow occur through the vessel. This may be viewed as a largely protective function against dramatic fluctuations in blood pressure and blood flow to maintain homeostasis. If perfusion of an organ is too low (ischemia), the tissue will experience low levels of oxygen (hypoxia). In contrast, excessive perfusion could damage the organ’s smaller and more fragile vessels. The myogenic response is a localized process that serves to stabilize blood flow in the capillary network that follows that arteriole.

When blood flow is low, the vessel’s smooth muscle will be only minimally stretched. In response, it relaxes, allowing the vessel to dilate and thereby increase the movement of blood into the tissue. When blood flow is too high, the smooth muscle will contract in response to the increased stretch, prompting vasoconstriction that reduces blood flow.

Figure 4 summarizes the effects of nervous, endocrine, and local controls on arterioles.
The heart is a muscle and, like any muscle, it responds dramatically to exercise. For a healthy young adult, cardiac output (heart rate × stroke volume) increases in the nonathlete from approximately 5.0 liters (5.25 quarts) per minute to a maximum of about 20 liters (21 quarts) per minute. Accompanying this will be an increase in blood pressure from about 120/80 to 185/75. However, well-trained aerobic athletes can increase these values substantially. For these individuals, cardiac output soars from approximately 5.3 liters (5.57 quarts) per minute resting to more than 30 liters (31.5 quarts) per minute during maximal exercise. Along with this increase in cardiac output, blood pressure increases from 120/80 at rest to 200/90 at maximum values.

In addition to improved cardiac function, exercise increases the size and mass of the heart. The average weight of the heart for the nonathlete is about 300 g, whereas in an athlete it will increase to 500 g. This increase in size generally makes the heart stronger and more efficient at pumping blood, increasing both stroke volume and cardiac output.

Tissue perfusion also increases as the body transitions from a resting state to light exercise and eventually to heavy exercise (see Figure 4). These changes result in selective vasodilation in the skeletal muscles, heart, lungs, liver, and integument. Simultaneously, vasoconstriction occurs in the vessels leading to the kidneys and most of the digestive and reproductive organs. The flow of blood to the brain remains largely unchanged whether at rest or exercising, since the vessels in the brain largely do not respond to regulatory stimuli, in most cases, because they lack the appropriate receptors.

As vasodilation occurs in selected vessels, resistance drops and more blood rushes into the organs they supply. This blood eventually returns to the venous system. Venous return is further enhanced by both the skeletal muscle and respiratory pumps. As blood returns to the heart more quickly, preload rises and the Frank-Starling principle tells us that contraction of the cardiac muscle in the atria and ventricles will be more forceful. Eventually, even the best-trained athletes will fatigue and must undergo a period of rest following exercise. Cardiac output and distribution of blood then return to normal.

Regular exercise promotes cardiovascular health in a variety of ways. Because an athlete’s heart is larger than a nonathlete’s, stroke volume increases, so the athletic heart can deliver the same amount of blood as the nonathletic heart but with a lower heart rate. This increased efficiency allows the athlete to exercise for longer periods of time before muscles fatigue and places less stress on the heart. Exercise also lowers overall cholesterol levels by removing from the circulation a complex form of cholesterol, triglycerides, and proteins known as low-density lipoproteins (LDLs), which are widely associated with increased risk of cardiovascular disease. Although there is no way to remove deposits of plaque from the walls of arteries other than specialized surgery, exercise does promote the health of vessels by decreasing the rate of plaque formation and reducing blood pressure, so the heart does not have to generate as much force to overcome resistance.

Generally as little as 30 minutes of noncontinuous exercise over the course of each day has beneficial effects and has been shown to lower the rate of heart attack by nearly 50 percent. While it is always advisable to follow a healthy diet, stop smoking, and lose weight, studies have clearly shown that fit, overweight people may actually be healthier overall than sedentary slender people. Thus, the benefits of moderate exercise are undeniable.
Any disorder that affects blood volume, vascular tone, or any other aspect of vascular functioning is likely to affect vascular homeostasis as well. That includes hypertension, hemorrhage, and shock.

A. Hypertension and Hypotension

New guidelines in 2017 from the American College of Cardiology and American Heart Association list normal blood pressure (BP) as less than 120/80 mm Hg and elevated BP as systolic P between 120–129 and diastolic P less than 80 mm Hg. Chronically elevated blood pressure is known clinically as hypertension. The new guidelines list hypertension that should be treated as 130/80 mm Hg. Tens of millions of Americans currently suffer from hypertension. Unfortunately, hypertension is typically a silent disorder; therefore, hypertensive patients may fail to recognize the seriousness of their condition and fail to follow their treatment plan. The result is often a heart attack or stroke. Hypertension may also lead to an aneurysm (ballooning of a blood vessel caused by a weakening of the wall), peripheral arterial disease (obstruction of vessels in peripheral regions of the body), chronic kidney disease, or heart failure.

B. Hemorrhage

Minor blood loss is managed by hemostasis and repair. Hemorrhage is a loss of blood that cannot be controlled by hemostatic mechanisms. Initially, the body responds to hemorrhage by initiating mechanisms aimed at increasing blood pressure and maintaining blood flow. Ultimately, however, blood volume will need to be restored, either through physiological processes or through medical intervention.

In response to blood loss, stimuli from the baroreceptors trigger the cardiovascular centers to stimulate sympathetic responses to increase cardiac output and vasoconstriction. This typically prompts the heart rate to increase to about 180–200 contractions per minute, restoring cardiac output to normal levels. Vasoconstriction of the arterioles increases vascular resistance, whereas constriction of the veins increases venous return to the heart. Both of these steps will help increase blood pressure. Sympathetic stimulation also triggers the release of epinephrine and norepinephrine, which enhance both cardiac output and vasoconstriction. If blood loss were less than 20 percent of total blood volume, these responses together would usually return blood pressure to normal and redirect the remaining blood to the tissues.

Additional endocrine involvement is necessary, however, to restore the lost blood volume. The angiotensin-renin-aldosterone mechanism stimulates the thirst center in the hypothalamus, which increases fluid consumption to help restore the lost blood. More importantly, it increases renal reabsorption of sodium and water, reducing water loss in urine output. The kidneys also increase the production of EPO, stimulating the formation of erythrocytes that not only deliver oxygen to the tissues but also increase overall blood volume. Figure 5 summarizes the responses to loss of blood volume.

C. Circulatory Shock

The loss of too much blood may lead to circulatory shock, a life-threatening condition in which the circulatory system is unable to maintain blood flow to adequately supply sufficient oxygen and other nutrients to the tissues to maintain cellular metabolism. It should not be confused with emotional or psychological shock. Typically, the patient in circulatory shock will demonstrate an increased heart rate but decreased blood pressure, but there are cases in which blood pressure will remain normal. Urine output will fall dramatically, and the patient may appear confused or lose consciousness. Urine output less than 1 mL/kg body weight/hour is cause for concern. Unfortunately, shock is an example of a positive-feedback loop that, if uncorrected, may lead to the death of the patient.

There are several recognized forms of shock:

  • Hypovolemic shock in adults is typically caused by hemorrhage, although in children it may be caused by fluid losses related to severe vomiting or diarrhea. Other causes for hypovolemic shock include extensive burns, exposure to some toxins, and excessive urine loss related to diabetes insipidus or ketoacidosis. Typically, patients present with a rapid, almost tachycardic heart rate; a weak pulse often described as “thready;” cool, clammy skin, particularly in the extremities, due to restricted peripheral blood flow; rapid, shallow breathing; hypothermia; thirst; and dry mouth. Treatments generally involve providing intravenous fluids to restore the patient to normal function and various drugs such as dopamine, epinephrine, and norepinephrine to raise blood pressure.
  • Cardiogenic shock results from the inability of the heart to maintain cardiac output. Most often, it results from a myocardial infarction (heart attack), but it may also be caused by arrhythmias, valve disorders, cardiomyopathies, cardiac failure, or simply insufficient flow of blood through the cardiac vessels. Treatment involves repairing the damage to the heart or its vessels to resolve the underlying cause, rather than treating cardiogenic shock directly.
  • Vascular shock occurs when arterioles lose their normal muscular tone and dilate dramatically. It may arise from a variety of causes, and treatments almost always involve fluid replacement and medications, called inotropic or pressor agents, which restore tone to the muscles of the vessels. In addition, eliminating or at least alleviating the underlying cause of the condition is required. This might include antibiotics and antihistamines, or select steroids, which may aid in the repair of nerve damage. A common cause is sepsis (or septicemia), also called “blood poisoning,” which is a widespread bacterial infection that results in an organismal-level inflammatory response known as septic shock. Neurogenic shock is a form of vascular shock that occurs with cranial or spinal injuries that damage the cardiovascular centers in the medulla oblongata or the nervous fibers originating from this region. Anaphylactic shock is a severe allergic response that causes the widespread release of histamines, triggering vasodilation throughout the body.
  • Obstructive shock, as the name would suggest, occurs when a significant portion of the vascular system is blocked. It is not always recognized as a distinct condition and may be grouped with cardiogenic shock, including pulmonary embolism and cardiac tamponade. Treatments depend upon the underlying cause and, in addition to administering fluids intravenously, often include the administration of anticoagulants, removal of fluid from the pericardial cavity, or air from the thoracic cavity, and surgery as required. The most common cause is a pulmonary embolism, a clot that lodges in the pulmonary vessels and interrupts blood flow. Other causes include stenosis of the aortic valve; cardiac tamponade, in which excess fluid in the pericardial cavity interferes with the ability of the heart to fully relax and fill with blood (resulting in decreased preload); and a pneumothorax, in which an excessive amount of air is present in the thoracic cavity, outside of the lungs, which interferes with venous return, pulmonary function, and delivery of oxygen to the tissues.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at openstax.org.

OrganResting
(mL/min)		Mild exercise
(mL/min)		Maximal exercise
(mL/min)
Skeletal muscle1200450012,500
Heart250350750
Brain750750750
Integument50015001900
Kidney1100900600
Gastrointestinal14001100600
Others
(i.e., liver, spleen)		600400400
Total5800950017,500

Adequate blood flow, blood pressure, distribution, and perfusion involve autoregulatory, neural, and endocrine mechanisms.

Increased blood pressure results in increased rates of baroreceptor firing, whereas decreased blood pressure results in slower rates of fire, both initiating the homeostatic mechanism to restore blood pressure.

In the renin-angiotensin-aldosterone mechanism, increasing angiotensin II will stimulate the production of antidiuretic hormone and aldosterone. In addition to renin, the kidneys produce erythropoietin, which stimulates the production of red blood cells, further increasing blood volume.

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Script:
  1. Neural, endocrine, and autoregulatory mechanisms affect blood flow, blood pressure, and eventually perfusion of blood to body tissues.
  2. Neural mechanisms include the cardiovascular centers in the medulla oblongata, baroreceptors in the aorta and carotid arteries and right atrium, and associated chemoreceptors that monitor blood levels of oxygen, carbon dioxide, and hydrogen ions.
  3. Endocrine controls include epinephrine and norepinephrine, as well as antidiuretic hormone, the renin-angiotensin-aldosterone mechanism, atrial natriuretic hormone, and erythropoietin.
  4. Autoregulation is the local control of vasodilation and constriction by chemical signals and the myogenic response.
  5. Exercise greatly improves cardiovascular function and reduces the risk of cardiovascular diseases, including hypertension, a leading cause of heart attacks and strokes.
  6. Shock is a critical condition characterized by inadequate tissue perfusion, leading to cellular dysfunction and organ failure.
  7. Distributive shock results from widespread vasodilation and increased capillary permeability, as seen in septic shock or anaphylaxis.
  8. Hypovolemic shock occurs due to a significant loss of intravascular volume, commonly from hemorrhage or dehydration.
  9. Cardiogenic shock stems from impaired cardiac function, often due to myocardial infarction or severe heart failure.
  10. Obstructive shock arises from physical obstruction of blood flow, such as in pulmonary embolism or cardiac tamponade.
  11. Each type of shock demands prompt recognition and appropriate intervention to mitigate its potentially life-threatening consequences.
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