chapter 20 a&p

vessel form

layers; connective tissue, smooth muscle, endothelium lining; sphincter muscles and smooth muscle direct blood flow

vessels are subject to these physical forces

pressure, gravity, viscosity of blood

what vessel has valves

veins

what are similar to veins

lymphatic vessels

arteries

carry blood away from the heart

arterioles

smaller in diameter, important in regulation of blood pressure

capillaries

exchange vessels; all chemical and gas exchange; critical for homeostasis

venules

lead from capillaries to veins

veins

carry blood to heart

vasa vasorum

Small blood vessels that supply the walls of larger arteries and veins

nervi vasorum

nerves which innervate arteries and veins

tunica intima

endothelium

tunica media

smooth muscle and elastic fibers

tunica externa

areolar connective tissue, elastic and collagen fibers; anchoring, large vessels with vasa vasorum

progression of arteries

large diameter to smaller diameter, decrease in elastic fibers, increase in smooth muscle

elastic arteries

nearest the heart, largest diameter, help propel blood from heart when ventricles are relaxing, helps maintain blood pressure

muscular arteries

medium sized, greater vasoconstriction and vasodilation, distribute blood to body, “pressure points” to reduce bleeding

atherosclerosis

injury to artery, inflammatory reaction, cholesterol adheres, foam cells (macrophages), smooth muscle invades, occlusion

aneurism

changes as we age, thinner which allows ballooning, prone to rupture, common in the aorta and arteries at the base of the brain

arterioles

small arteries that deliver blood to the capillaries, key role in regulating blood flow by regulating resistance

vasoconstriction

decreased blood flow = increased blood blow

vasodilation

increased blood flow = decreased blood pressure

continuous capillaries

tight junctions, often incomplete; allows movement of water, ions, hormones, glucose; most common; prevent loss of blood and plasma protein; found in all tissues except cartilage and epithelia; endothelium complete

fenestrated capillaries

regions of thin endothelial cells (fenestration), allows movement of plasma proteins, fluid transport with interstitial fluid, small intestine, eye, and choroid plexus, pore-containing capillaries, allow rapid exchange of water and solutes between plasma and interstitial fluid

sinusoids

permits free exchange of large solutes and water between blood and interstitial fluid, red bone marrow and liver and spleen and endocrine glands, capillaries with gaps between cells

venues

smallest veins, with capillaries, area of leukocyte diapedesis

veins

valves to prevent back flow, blood resevoirs

blood volumes

systemic circulation: 70%

veins: 55%

end arteries

single connection to tissue, do not connect with other capillaries

anastomoses

joining together of blood vessels

portal systems

2 capillary beds separated by a portal vein; hypophyseal portal system (in brain), hepatic portal system (small intestine and spleen to liver)

brachial artery

measuring blood pressure

carotid arteries

measure pulse in neck

radial artery

measure pulse in wrist

circle of willis

redundancy of blood supply to brain

capacitance vessels

pooling of blood

where is most of the blood distribution

veins

venous reserve

liver, bone marrow, integument

what does venoconstriction do

speed blood flow back to heart

blood pressure

originating with ventricular contraction, form of hydrostatic pressure, pressure gradient from aorta to veins to RA, altered by CO

arterial pressure

pulse pressure; 120-40mmHg

venous pressure

20-0mmHg

factors affecting blood flow

CO, compliance (ability to expand without resistance), blood volume, blood viscosity, blood vessel structure (length and diameter)

cross sectional area

total area is largest for capillaries bc there are so many of them, inverse relationship with blood flow velocity, pressure is also decreasing from aorta to the vena cavae

factors in resistance to blood flow

blood viscosity, blood vessel length, side of lumen (laminar flow)

how is flow related to pressure changes

directly

how is flow related to resistance

indirectly

how are CO, resistance, and blood volume related to pressure

directly

venous pressure

16-20mmHg

venous return

skeletal muscle pump, respiratory pump

effects of constriction in arteries

vasoconstriction causes an increase in pressure and a decrease in blood flow

effects of constriction in veins

venoconstriction causes an increase in pressure and blood flow (due to the activation of smooth muscle which smooths the lining of veins reducing resistance to flow)

hydrostatic pressure

from fluid., drives fluid into tissues

osmotic pressure

from solutes, drives reabsorption

how much fluid does the lymphatic system resorb

about 15%

starling’s law

end diastolic volume = venous return, affects CO thru SV

pulmonary arteries

less elastic connective tissue, wider lumens, shorter, lower pressure

myogenic response

smooth muscle in afferent arterioles, increased BP increases constriction

vasoactive chemicals

vasodilators and vasoconstrictors

degree of vascularization

angiogenesis and regression (narrowing and retraction of blood vessel)

factors affecting blood flow

HR/mL per minute, degree of vascularization, myogenic response, local regulation

autoregulation

response to changes in metabolic activity, reactive hyperemia (more blood flow in a tissue/organ or to intestines after a meal)

vasodilation

inflammation (prostaglandins)

vasoconstriction

epinephrine and norepinephrine

neural regulation of blood flow and pressure

cardiovascular center in medulla oblongata, receptors in vessels, higher brain centers

cardiovascular center in medulla oblongata

cardiac center: regulates HR

vasomotor center: blood vessel diameter

receptors in vessels

baroreceptors: initiate reflexes

chemoreceptors: detect changes in acidity (C)2) and O2 levels

higher brain centers

hypothalamus: respond to body temp involving the HR

ANS: sympathetic and parasympathetic responses

limbic system: emotional centers

renin-angiotensin system

raises blood pressure, initiated by nervous system

liver: continually released angiotensinogen

kidney: releases renin in response to pressure changes

blood: conversion by renin of angiotensinogen to angiotensin I

capillaries: angiotensin converting enzyme (ACE) to angiotensin II

hormonal regulation

alters resistance or blood pressure or both

aldosterone

increases Na+ and H2O absorption in kidneys

antidiuretic hormone (ADH)

maintains blood volume and pressure

atrial natriuretic peptide (ANP)

decreases pressure