Module 3: Circulatory System Flashcards
principle of circulatory system
continuous movement of body fluids
transport of oxygen and nutrients to tissues
Transport of CO2 and other metabolic waste products from tissues
Temp regulation
Distribution of molecules (hormones, immune system cells)
Made up of cardiovascular and lymphatic system
Lymphatic system
made up of lymphatic vessels and lymph nodes
Vessels drain excess tissue fluids from interstitial tissues at capillary beds to form lymph (when venous side of capillary bed does not reabsorb the tissue fluid)
Lymph filtered through lymph nodes and returned to blood
What is lymph composed of
water, lytes, protein plasma
metabolic wastes, leukocytes, lipids
Lymphatic capillaries
collection of excess tissue fluid and protein
Thin wall thickness
Basement membrane may not be continuous =
NO tunica media
Tunica adventitia is very thin (only trace amounts of connective tissue)
Large lymphatic vessels
carry lymph through the system to the ducts where they empty into the bloodstream
Thin wall thickness
Tunica intima consists of endothelium with some elastic tissue and valves
Tunica media is a few layers of smooth muscle and connective tissue
Tunica adventitia is slightly thicker (smooth muscle and connective tissue)
3 layers of walls of heart, blood vessels, lymphatics
INNER Tunica Intima Tunica Media Tunica Adventitia OUTER
Tunica intima
innermost lining
single layer of flattened epithelial cells (endothelium)
Supported by basement membrane and some connective tissue
Ex. Endocardium of heart
Tunica Media
middle layer of muscle
Smooth muscle fibers in vessels as well as elastin
Not present in small vessels and capillaries
Ex. myocardium of heart
Tunica Adventitia
Outer loose connective tissue
ex. epicardium
Arteries
distributes blood from heart to capillary beds throughout body
Cyclic pumping action produces blood flow
Expansion and recoil of arterial wall is facilitated by elastic tissue in walls
Flow regulated by controlling diameter of vessels (by sympathetic nervous system and adrenal medullary hormones)
Elastic arteries
major distribution vessels that maintain diastolic pressure
Ex. Aorta, carotid and subclavian artery and most pulmonary arterial vessels
Substantially thicker tunica intimate (Elastic fibres and smooth muscle) than muscular arteries
Tunica Media is major portion of wall (elastic lamina between layers of smooth muscle)
Tunica Adventitia: Thinnest layer (elastic and collagen fibres)
Muscular arteries
main distributing branches of arterial tree
Ex. Radial arteries
Function: Move blood under high pressure to all parts of body
Tunica intima: Thin with internal elastic lamina
Tunica Media: smooth muscle with some elastic fibres in larger vessels
Tunica Adventitia: variable thickness, composed of elastic and collagen fibers
Arterioles
terminal branches of arterial tree
Reduce pressure and regulate blood supply to capillary beds
Tunica intima: Thin with internal elastic lamina (absent in small vessels)
Tunica media: Thickest layer, smooth muscle fibres
Tunica adventitia: Thin; collagen and elastic fibers
Transition between arterial types is
gradual
Capillaries
smallest arteriole → capillary → venuole
Nutrients and oxygen to cells of body, and taking away waste products
Only slightly larger than diameter of RBC
total wall thickness is very thin
Tunica intima: very thin
Tunica media: absent
Tunica adventitia: Very thin, only a few fibres of connective tissue
Metarterioles
slightly larger capillaries
Similar structure to capillaries but have a discontinuous layer of smooth muscle cells
Veins
return blood to heart
low pressure collecting system
respiratory inspiration → negative pressure within the thorax and within the right atrium of heart
Venues return from extremities aided by contraction of skeletal muscles
Expiration → pressure gradient is reversed and blood tends to flow in opposite direction (prevented from doing so by presence of valves)
Venules
collection of blood from capillaries
release plasma and WBC into tissues (acute inflammatory response)
Total thickness is THIN
Tunica intima: thin (endothelium and basement membrane)
Tunica media: Absent in small venules; 1-2 layers of smooth muscle in larger venules
Tunica adventitia: very thin layer of collagen fibers
Small and medium veins
carry blood under low pressure to the heart
Total thickness is THIN
Tunica intima: endothelial lining, basement membrane, small amount of connective tissue and elastic lamina with valves present in med veins
Tunica media: thin, smooth muscle with some connective and elastic fibres
Tunica adventitia: thick, both connective and elastic fibers
large veins
return of blood under reduced pressure to heart (ex. vena cava)
Overall vessel wall is thin
Tunica intima: thin, endothelium, basement membrane, some connective and elastic fibers
Tunica media: thin, few layers of smooth muscle and some elastic fibres
Tunica adventitia: thick, smooth muscle, collagen and elastic fibers
Vasa vasorum
provides blood distribution to large blood vessels
“blood supply to the tissue of the vessel”