Chapter 20: Blood Vessels and Circulation Flashcards

Comprehensive vocabulary flashcards covering blood vessel structure, hemodynamics, capillary exchange, regulatory mechanisms, systemic and pulmonary pathways, and fetal circulation from Chapter 20.

Tunica Intima

The innermost layer of a blood vessel wall composed of an endothelium of simple squamous epithelium and a subendothelial layer of areolar connective tissue.

Tunica Media

The middle layer of a blood vessel wall consisting of circularly arranged smooth muscle cells with elastic fibers; contraction causes vasoconstriction and relaxation causes vasodilation.

Tunica Externa

The outermost layer of a blood vessel wall composed of areolar connective tissue with elastic and collagen fibers that helps anchor the vessel to adjacent structures.

Vasa Vasorum

A network of small blood vessels located within the tunica externa that supply blood to the walls of large blood vessels.

Elastic Arteries

The largest arteries, ranging from $2.5\,cm$ to $1\,cm$ in diameter, containing a high proportion of elastic fibers to accommodate stretch and recoil while conducting blood away from the heart.

Muscular Arteries

Medium-sized arteries, ranging from $1\,cm$ to $0.3\,mm$ in diameter, that distribute blood to specific body regions and feature internal and external elastic laminae.

Arterioles

The smallest arteries, with diameters ranging from $0.3\,mm$ to $10\,\mu m$, that regulate systemic blood pressure and blood flow into capillary beds.

Vasomotor Tone

The state of partial constriction maintained in arteriole smooth muscle, regulated by the vasomotor center in the brainstem.

Atherosclerosis

A progressive disease of elastic and muscular arteries characterized by atheroma formation, thickening of the tunica intima, and narrowing of the arterial lumen.

Aneurysm

A localized thinning and ballooning of an arterial wall that renders the vessel wall prone to rupture.

Continuous Capillaries

Capillaries featuring a continuous lining of endothelial cells connected by tight junctions with intercellular clefts that allow small solutes like glucose to pass.

Fenestrated Capillaries

Capillaries with continuous endothelial linings containing fenestrations (pores) that permit the movement of smaller plasma proteins, commonly found in the intestines and kidneys.

Sinusoids

Capillaries with an incomplete endothelial lining, large gaps, and an incomplete or absent basement membrane, allowing the passage of large substances such as formed elements and large plasma proteins.

Precapillary Sphincter

A smooth muscle ring located at the origin of a true capillary that relaxes or contracts to control blood flow into the capillary bed.

Vasomotion

The cyclical process of contraction and relaxation of precapillary sphincters within a capillary bed.

Perfusion

The amount of blood entering capillaries per unit time per gram of tissue, expressed in $mL/min/g$.

End Artery

An artery that provides the sole pathway of blood supply to a specific organ or body region.

Arterial Anastomosis

An alternative vascular pathway where two or more arteries converge to supply the same body region.

Arteriovenous Anastomosis

A vascular shunt that transports blood directly from an artery into a vein, bypassing a capillary bed.

Portal System

An alternative blood flow pathway where blood passes through two capillary beds in sequence (artery \rightarrow capillary bed \rightarrow portal vein \rightarrow capillary bed \rightarrow vein).

Bulk Flow

The movement of large amounts of fluids and dissolved substances down a pressure gradient across the capillary wall.

Filtration

The movement of fluid and small solutes out of the blood into the interstitial fluid at the arterial end of a capillary, driven by hydrostatic pressure.

Reabsorption

The movement of fluid back into the blood from the interstitial fluid at the venous end of a capillary, driven by colloid osmotic pressure.

Blood Hydrostatic Pressure ($HP_b$)

The force exerted per unit area by blood against a blood vessel wall, which promotes filtration out of capillaries.

Blood Colloid Osmotic Pressure ($COP_b$)

The osmotic pull that draws fluid back into blood vessels due to the concentration of blood proteins such as albumins.

Net Filtration Pressure (NFP)

The net pressure difference governing fluid movement across capillaries, calculated as $NFP = (HP_b - HP_{if}) - (COP_b - COP_{if})$.

Angiogenesis

The formation of new blood vessels in a tissue over weeks or months to increase potential perfusion.

Myogenic Response

The intrinsic contraction or relaxation of vascular smooth muscle in response to changes in stretch to maintain constant local blood flow.

Autoregulation

The process by which a tissue self-regulates its local blood flow in response to changing metabolic demands.

Reactive Hyperemia

A temporary increase in local blood flow to a tissue following a period of restricted or disrupted blood flow.

Systolic Pressure

The peak arterial blood pressure recorded during ventricular contraction (systole) when the arterial wall is maximally stretched.

Diastolic Pressure

The minimum arterial blood pressure recorded during ventricular relaxation (diastole) when the arterial wall recoils.

Pulse Pressure

The additional pressure placed on arteries during heart contraction, calculated as $\text{Pulse Pressure} = \text{Systolic Pressure} - \text{Diastolic Pressure}$.

Mean Arterial Pressure (MAP)

The average blood pressure within the arterial system across the entire cardiac cycle, calculated as $\text{MAP} = \text{Diastolic Pressure} + \frac{1}{3}(\text{Pulse Pressure})$.

Skeletal Muscle Pump

A mechanism aiding venous return from the extremities in which contracting skeletal muscles squeeze veins and drive blood past one-way valves toward the heart.

Respiratory Pump

A mechanism assisting venous return in the trunk driven by pressure changes in the thoracic and abdominal cavities during inspiration and expiration.

Peripheral Resistance

The friction encountered by blood as it moves through blood vessels, affected by blood viscosity, vessel length, and vessel radius.

Baroreceptors

Specialized sensory nerve endings located in the tunica externa of the aortic arch and carotid sinuses that monitor blood pressure by detecting vessel wall stretch.

Renin-Angiotensin System

A hormonal pathway initiated by kidney release of renin in response to low blood pressure, converting angiotensinogen to angiotensin I, which is converted by ACE to angiotensin II.

Angiotensin II

A potent vasoconstrictive hormone that increases blood pressure by raising peripheral resistance, stimulating the thirst center, and decreasing urine formation.

Aldosterone

A hormone secreted by the adrenal cortex that increases renal absorption of sodium ions and water, conserving blood volume and raising blood pressure.

Antidiuretic Hormone (ADH)

A hormone released from the posterior pituitary that increases water reabsorption in the kidneys, stimulates thirst, and causes vasoconstriction in large concentrations.

Atrial Natriuretic Peptide (ANP)

A hormone released from the heart's atria in response to high blood volume that lowers blood pressure by inducing vasodilation and increasing urine output.

Pulmonary Circulation

The cardiovascular circuit that transports deoxygenated blood from the right ventricle to the lungs for gas exchange and returns oxygenated blood to the left atrium.

Cerebral Arterial Circle

An arterial anastomosis at the base of the brain around the sella turcica, also known as the circle of Willis, that equalizes blood pressure and provides collateral pathways.

Dural Venous Sinuses

Large, modified venous channels located between layers of dura mater in the cranial cavity that collect venous blood and excess cerebrospinal fluid to drain into the internal jugular veins.

Azygos System

A network of veins including the azygos, hemiazygos, and accessory hemiazygos veins that drains blood from the thoracic and abdominal walls into the superior vena cava.

Celiac Trunk

An unpaired artery originating from the abdominal aorta just inferior to the diaphragm that branches into the left gastric, splenic, and common hepatic arteries.

Superior Mesenteric Artery

An unpaired branch of the abdominal aorta supplying blood to the small intestine (jejunum and ileum), ascending colon, most of the transverse colon, cecum, and appendix.

Inferior Mesenteric Artery

An unpaired branch of the abdominal aorta supplying blood to the distal transverse colon, descending colon, sigmoid colon, and upper rectum.

Hepatic Portal System

A venous circulation pathway that routes nutrient-rich blood from the digestive organs and spleen through the hepatic portal vein into liver sinusoids before reaching the inferior vena cava.

Internal Iliac Artery

A branch of the common iliac artery serving as the primary arterial supply to the pelvic organs, gluteal muscles, and perineum.

Great Saphenous Vein

A superficial vein originating at the medial ankle that extends along the medial surface of the lower limb before draining into the femoral vein.

Ductus Venosus

A fetal vascular shunt that directs oxygenated blood from the umbilical vein directly into the inferior vena cava, bypassing the liver.

Foramen Ovale

An opening in the fetal interatrial septum that shunts blood directly from the right atrium to the left atrium, bypassing the nonfunctional lungs.

Ductus Arteriosus

A fetal blood vessel connecting the pulmonary trunk to the aorta to shunt blood away from the nonfunctional lungs.

Fossa Ovalis

An oval depression in the adult interatrial septum representing the closed remnant of the fetal foramen ovale.

Ligamentum Arteriosum

A fibrous cord connecting the aortic arch and pulmonary trunk in adult anatomy, formed by the closure of the fetal ductus arteriosus.