Circulatory System

Blood Circulatory System-arterial system-capillaries-venous system

Lymphatic System-capillaries and ducts-lymphatic organs

spleen, tonsils, thymus, lymph nodes

Arteries* and Veins: Three layerstunica intima

squamous epitheliumbasal laminasubendothelial layer

*internal elastic membrane

tunica mediasmooth muscle

*external elastic membrane

tunica adventitia

connective tissuevasa vasorumnervi vascularis

Arterieselastic arteries (large:aorta, pulmonary

vein)

reduced internal elastic membrane tunica media- elastic fibers, smooth

muscle

muscular arteries (medium)prominent internal elastic membrane tunica media:>smooth muscle

<elastic fibers

small arteries/ arteriolesclassified by # smooth muscle layers

arterioles 1-2; small artery 3-8precapillary sphincter- smooth

muscle

Aorta

Medium artery

arteriole

Venous System

Large veins: 3 layers not distinctlumen larger than arterylumen often collapsedvalves

Medium veins: similar to large vein structure adventenia thicker than media

several layers of muscle

Venules: postcapillary- fluid/cell loss - histamine

muscular: 1-2 layers of muscle

Vein Artery

Vein3 layers not as distinctlumen larger than arterylumen often collapsedvalves

Vein and valve

venule

arteriole

capillary

Medium artery

vein

Capillaries

- simple squamous epithelium- no smooth muscle- basal lamina (basement membrane)- pericytes within basal lamina

- large surface area for exchange - primary site of exchange for fluid electrolytes, gases, and

macromolecules

Capillary Bed

Capillaries

Types:continuousfenestrateddiscontinuous (sinusoidal)

Continuous Capillaries

- close cellular interconnections

•junctional complexes

- permeable to small molecules <10nm in diameter

- most transport via pinocytotic vesicles

- muscle, skin, lungs, adipose tissue, CNS*, retina and mammary glands

Transcellular Transport- pinocytotic vesicles

Junctional Complex - zonula occludens - zonula adherens - desmosome

apical

basal

Pericyte: undifferentiated cell with multiple processes give rise to new endothelial cells

contained within basal lamina

Fenestrated Capillaries

-contain 'windows’, fenestrations- easy passage of larger molecules (10-

100nm) - number of fenestrations varies with absorption - pinocytotic vesicles- diaphragms

-nonmembranous- basal lamina intact- kidneys, pancreas, gallbladder, intestine

Continuous capillary

Fenestrated capillary

Discontinuous (sinusoidal) Capillaries

- large diameter- wide gaps between cells- relatively free movement (even cells)- gaps or missing basal lamina- liver, spleen, ovaries, some endocrine

glands

PERMEABILITY

Low High Extremely

High

Blood flow through Capillary Bed

-controlled by precapillary sphincters

-smooth muscle band at arteriole/capillary

fajerpc.magnet.fsu.edu/.../ 30_Circulatory.htm

Fluid Movement across Capillary Wall: Starling’s Law of Capillaries

- Governed by Hydrostatic and Osmotic Pressures

Capillary Hydrostatic Pressure (HP): blood pressure

forces fluid OUT

Osmotic Pressure (OP): pressure due to plasma

proteins trapped in capillary

draws fluid IN

HP > OP -->fluid moves from cap to tissue-->FILTRATION occurs at arteriole end of capillary

HP < OP-->fluid moves from tissue to cap->REABSORPTION occurs at venous end of capillary

SMALL NET LOSS OF FLUID FROM BLOOD

Residual Fluid is taken up by Lymphatic Capillaries

-lymphatic ducts-returned to blood

Lymphatic Capillaries and Vessels

-blind end capillaries

-interstitial fluid pressure drives lymph into lymph capillary

Lymphatic Capillaries and Vessels

- one cell thick: overlapping pattern– shingles

- one-way valves ensure flow away from tissues

Lymphatic Capillaries and Vessels

- one cell thick: overlapping pattern– shingles

- one-way valves ensure flow away from tissues

Lymphatic Capillaries and Vessels

The flow of lymph is regulated by:

1. Skeletal Muscle Pump.

2. Respiratory Pump.

3. Contraction of smooth muscle in larger lymphatic vessels walls

4. Pressure on lymphatic vessels by expansion/recoil of nearby arteries

Skeletal muscle pumpwww.cvphysiology.com/ Cardiac%20Function/CF018.htm

A. A 62 year old woman has marked swelling of ankles and lower legs. Form a hypothesis stating what you think could account for this symptom.

B. Design an experiment that will test your hypothesis.

Edema: accumulation of fluid in interstitial spaces

Hypotheses:

1. Increased capillary hydrostatic pressure - gravitational forces- in heart failure

2. Decreased osmotic pressure- loss of plasma proteins from kidney or liver disease

3. Increased capillary permeability- inflammatory compounds- histamine, Anaphylaxis- trauma- burns

4. Lymphatic obstruction (as occurs in filariasis)- side effect of surgery- Elephantiasis (filariasis)

Lymphatic filariasis (elephantiasis)

- caused by parasitic worm, Wuchereria bancrofti

- transmitted to humans by mosquitoe bites

- painful, disfiguring chronic enlargement of arms, legs

and genitals

Lymphangiogram

Visualization of lymph system of legs

Inject dye between toes, visualize lymph

vessel

Inject dye directly into lymph vessel

Image dye-stained lymphatic system

Capillary PermeabilityInject tracers of variable sizes

Identify location within and outside vessels

Lymphatic System

- monitor body surfaces and internal fluids

- react to potentially harmful substances

Lymphatic Tissues

- Concentrated nearrespiratory tract

digestive tractreproductive tract

Antigen: foreign substance

First Encounter->Nonspecific Inflammatory Response

Mast cells-Histamine release-Vasodilation-Increase permeability

Neutrophils-enzymatic digestion of virus

Macrophages-cytokine release-phagocytosis-antigen presentation