Chp 19 part 1 Flashcards
what is the lumen
Space inside the vessel mostly occupied by blood.
3 layers of wall structures
Tunica intima(interna)
Tunica media
Tunica adventitia(externa)
list the layers of the tunica intima
Endothelium
Sub-endothelia layer
Internal elastic lamina
describe their tissue structure and position (superficial versus deep)
Endothelium (next to the lumen); layer of simple squamous epithelium
Sub-endothelia layer (superficial to endothelium); made of connective tissue; contains a lot of collagen
Internal elastic lamina (superficial to sub-endothelia layer); network of elastic fibers
what is the significance of collagen in sub-endothelial layer?
Protects against unwanted blood clotting
arrangement of the smooth muscle cells:
Arranged in a circular pattern
what is the function of smooth muscle in the tunica media?
contract= constrict the vessel reducing blood flow but increasing blood pressure
relax= they dilate the blood vessel increasing blood flow but decreasing blood pressure.
What controls contraction of smooth muscle
ANS and chemical messengers
what is the function of elastic fibers in the tunica media
Allow vessel to expand and recoil
which vessels have an external elastic lamina?
Elastic and muscular arteries
describe the tunica adventitia (location and tissue structure):
Most superficial layer of a blood vessel; dense irregular c.t. supports blood vessel wall
where are the vasa vasora and what is their function
Small blood vessels, Perfuse the tunica media and the tunica adventitia
basic function for each of the three major vessel types
-arteries: carry blood away from the heart
-capillaries: allow exchange of materials between blood and tissue fluid
-veins: return blood to the heart
how does the wall, size and shape of an artery differ from those of a vein?
the walls are thicker
why do arteries have thick walls?
blood is under higher pressure
elastic / conducting arteries Size and diameter
Largest in diameter; closest to the heart
What is the function of elastic / conducting arteries
distribute blood to major region of body
composition of tunica media in elastic/ conducting arteries
circular sheets of elastin fibers with almost no smooth muscle
what happens during diastole of elastic/ conducting arteries
Recoil to maintain blood pressure
muscular arteries size and location:
Middle size; distal to elastic arteries
composition of tunica media in muscular arteries
Very thick;mostly smooth muscle with elastic fibers
What is the function of muscular arteries
Dialate and constrict to Regulate blood flow to individual organ
arterioles arteries Size
Smallest arteries
composition of tunica media in arteriole arteries
only smooth muscle
What is the function of arteriole arteries
Determines blood flow and blood pressure
What controls arteriole arteries
ANS and chemical messengers
size and structure of capillaries
Smallest blood vessels; consist of endothelial layer and a basal laminae only; NO TUNICA MEDIA or ADVENTITIA; diameter is 8-10 micrometers
how are the endothelial cells held together in capillaries
Joined around their edges by tight junctions and desmosomes
describe intercellular clefts
Opening between the cell junctions
describe pericytes
Cells located between the endothelial cells and the basal laminae that surrounds the capillary
three typesetting of capillaries
Continuous capillaries
Fenestrated capillaries
Sinusoids
Continuous capillaries
Intracellular clefts but no fenestra
permeability varies with their number and type of tight junctions that join the endothelial cells together
- least permeable are in the blood brain barrier where there are no intracellular clefts and almost continuous tight junctions
fenestrated capillaries
High permeability
Fenestrated
intracellular clefts found in small intestines, synovial joints, and kidneys
sinusoids
wide leaky capillaries
fenestrated
fewer cell junctions
very large intracellular clefts
found wherever the passage of large particles through the capillary wall is necessary
e.g. bone marrow ,spleen, and liver
describe the structure of a capillary bed:
NOT LINEAR branching networks that run between a met arteriole and a venule
how is flow through capillaries controlled?
small rings of smooth muscle called PRECAPILLARY SPHINCTERS
what is an anastomosis and their function
Occurs when vessels join mid stream Provide alternate passage for blood flow called COLLATERAL CHANNELS
Pulmonary circuit
pressure: low
driven by: right ventricle
function: takes blood to the lungs to pick up oxygen and to get rid of carbon dioxide
oxygen level in arteries: low; not full; 75%
oxygen level in veins: high;98%
Systemic circuit
functions: Perfuses the body with high oxygen, low carbon dioxide blood
-distributes nutrients from the digestive track to the body and collects waste and takes them to the kidney for excretion
pressure: high; 95-100 millimeters of mercury
-large pressure gradient is needed to push blood from heart to every tissue in the body and then back to the heart
driven by: contraction of the left ventricle
arteries that supply the circle of Willis
L/R internal carotid arteries, vertebral arteries
describe the location of the vertebral arteries in circle of Willis
Pass transverse foramina of the cervical vertebrae on their way up to the cranium
path of internal carotid a.:
Enters the skull through the carotid canal and divides into the anterior and middle cerebral arteries
path of internal carotid a.:
Enters the skull through the carotid canal and divides into the anterior and middle cerebral arteries
path of vertebral a.:
Enter the skull through the frame and magnum, and run anteriorly until the anastomose, inferior to the medulla oblongada
what is the function of the hepatic portal system
Picks up materials from the digestive system and takes them directly to the liver
