Blood Vessels and Circulation

Flashcards for review of blood vessels and circulation

Arteries

Carry blood away from the heart.

Arterioles

Smaller branches of arteries.

Capillaries

Smallest vessels where gas, nutrient, and waste exchange occur.

Venules

Small vessels that receive blood from capillaries and transport it back to the heart.

Veins

Large vessels that return blood to the heart.

Tunica intima

Innermost layer of vessel walls, including the endothelial lining and connective tissue with elastic fibers; contains internal elastic membrane in arteries.

Tunica media

Middle layer of vessel walls containing smooth muscle and loose connective tissue, allowing vasoconstriction and vasodilation; separated by external elastic membrane.

Tunica externa

Outermost layer of vessel walls, a connective tissue sheath of elastic and collagen fibers; thickest layer in veins.

Vasa vasorum

Vessels that supply blood to the cells of the vessel walls.

Vasoconstriction

Constriction of smooth muscle in artery walls, decreasing lumen and blood flow, thus increasing afterload. Controlled by the sympathetic division of the ANS.

Vasodilation

Relaxation of smooth muscle in artery walls, increasing lumen and blood flow, thus decreasing afterload. Controlled by the sympathetic division of the ANS.

Elastic arteries

Large arteries transporting large volumes of blood away from the heart; high elastic fiber concentration allows for elastic rebounding.

Muscular arteries

Medium-sized arteries distributing blood to skeletal muscles and internal organs; thick tunica media with high smooth muscle concentration.

Arterioles

Small arteries with poorly defined tunica externa; more muscle than elastic arteries; vasodilate when O2 levels are low and vasoconstrict under sympathetic stimulation.

Resistance (R)

Force opposing blood flow in arterioles; arterioles are also called resistance vessels.

Aneurysm

Bulge in the weakened wall of an artery; dangerous due to the possibility of rupture, internal bleeding, shock, and death. Most serious locations are in the brain and the abdominal aorta.

Arteriosclerosis

Thickening and hardening of the arterial walls.

Focal calcification

Deposition of Ca2+ salts following the degeneration of smooth muscle in the tunica media. Associated with diabetes and aging.

Atherosclerosis

Deposition of lipid in the tunica media (plaque) associated with damage to the endothelium. Increased with hypercholesterolemia, hypertension, smoking, diabetes, obesity, stress, Chlamydia, and birth control pills (estrogens slow plaque formation).

Capillaries

Microscopic vessels weaving through tissues forming extensive networks; walls are permeable, allowing exchange between blood and interstitial fluid.

Continuous capillaries

Capillaries with a complete endothelial lining, permitting diffusion of water, small solutes, and lipid-soluble materials; located in all tissue except epithelium and cartilage.

Fenestrated capillaries

Capillaries containing pores in the endothelium, permitting rapid exchange of water and large solutes; found in the choroid plexus and endocrine organs.

Capillary bed

Network of capillaries where the arterial and venous systems meet forming an anastomosis.

Angiogenesis

Formation of new blood vessels in response to tissue hypoxia.

Venules

Smallest type of veins beginning at the capillary beds; may lack a tunica media and contain valves.

Capillary blood flow

Determined by the interplay between pressure (P) and resistance (R) in the cardiovascular system.

Pulse

Rhythmic pressure oscillation that accompanies each heartbeat.

Hypertension

Blood pressure over 140/90.

Hypotension

Abnormally low blood pressure.

Tachycardia

A pulse over 90/min.

Bradycardia

A pulse under 60/min.

Venous return

Return of blood to the right atrium due to low resistance, convergence of the veins, and the presence of valves.

Muscular compression

Contractions of skeletal muscles surrounding the veins help push blood toward the heart.

Respiratory pump

As we inhale, the thoracic cavity expands pulling air into the lungs and blood from smaller veins into the inferior vena cava. Then as we exhale, air is forced out of the lungs, blood is pushed from the inferior vena cava into the right atrium.

Capillary Exchange

Process responsible for providing the body’s tissues with the materials they need to live and removing their waste.

Diffusion in Capillary Exchange

Occurs through adjacent endothelial cells or pores of the fenestrated capillaries (water, ions, glucose, amino acids, urea, lipids, O2, CO2), or through ion channels in the plasma membrane of the endothelial cells (Na+, K+, Ca2+). Large substances such as RBCs or plasma proteins are normally unable to diffuse out.

Filtration in Capillary Exchange

The retention of solutes as a solution flows across a porous membrane. This occurs with large solutes that cannot cross the endothelium. The driving force is the blood pressure within the capillary beds called hydrostatic pressure.

Reabsorption in Capillary Exchange

Occurs as osmosis, where a solvent (water) diffuses to an area of higher solute concentration.

Edema

Abnormal accumulation of interstitial fluid due to a disruption in homeostasis.

Autoregulation (Cardiovascular Regulatory Mechanisms)

Local factors or chemical changes in the interstitial fluid may have an effect on sphincters found within the capillary beds. Factors may be vasodilators (decreased tissue O2, lactic acid formation, histamine, increased temperature), or vasoconstrictors (prostaglandins, thromboxanes).

Neural mechanisms (Cardiovascular Regulatory Mechanisms)

Adjusts cardiac output and peripheral resistance by controlling the force and rate of the heart contraction, vasoconstriction and vasodilation. Located in the medulla oblongata and influenced by the ANS.

Endocrine mechanism (Cardiovascular Regulatory Mechanisms)

CO and BP can also be influenced by certain hormones. If BP is too high, atrial natriuretic peptide is released by the fibers in the right atrial wall and increases urine production by the kidneys. If the BP is too low, ADH (from neurohypophysis), angiotensin II and erythropoetin (from kidneys) are produced.

Pulmonary Circuit

The right ventricle receives deoxygenated blood from the right atrium, then this blood through the pulmonary semilunar valve into the pulmonary trunk, which curves over the superior border of the heart before diverging into the left and right pulmonary arteries (still carrying deoxygenated blood) and continues until gas exchange occurs at the microscopic alveoli where the blood becomes oxygenated.

Systemic Circuit

Left ventricle pumps the oxygenated blood through the aortic semilunar valve into the ascending aorta.

Superior Vena Cava

A great vein that drains into the right atrium and receives blood from the tissues and organs of the head, neck, chest, shoulders and upper limbs.

Cranial Sinuses

Largest sinus is the superior sagittal sinus found in the falx cerebri in the longitudinal fissure. receives blood from the majority of the cerebrum. Posteriorly, this sinus is continuous with the straight sinus located between the cerebrum and cerebellum and receives blood from the inferior cerebrum

Hepatic Portal System

System that begins in the capillaries of the GI tract and ends in the liver, contains high concentrations of dietary substances absorbed from the stomach and intestines (glucose, amino acids).

Foramen ovale

Hole in the interatrial septum

Ductus arteriosus

Duct that connects the pulmonary and aortic trunks