Lecture 7 Flashcards
What are capillaries?
Sites of exchange between blood and tissues
What are the functional demands of capillaries?
Very Thin walls
Large cross sectional area of capillary bed
Slow and smooth blood flow
What allows for slower blood flow to occur?
Large total area of capillary bed compared to arterioles
Structure of Capillaries?
Endothelial cells that lines cardiovascular system wrapped around to form a tube and bonding ti neighbours to form cellular pipe. Lumen is only the size of a red blood cell so that erythrocytes can only travel single file
Why do red blood cells travel single file down the capillary?
Makes distance for gas exchange down the tube as small as possible and therefore more efficient
What is the purpose of intercellular junctions in capillaries?
tight junctions fuses the capillary wall to itself to seal the tube
What is the supply pathway to capillary beds?
Terminal arterioles
What is the drainage network from capillary beds?
Postcapillary venule
What are precapillary sphincters?
Rings (involuntary muscle) that branch off the arterioles running into the capillary beds
What is the role of Precapillary sphincters
Constrict and stop blood from going into capillary beds
What is a vascular shunt?
Pathway that allows blood to pass from the arterioles to the venules without going through the exchange surfaces
What factors can cause capillary structure to vary?
The structure of capillaries varies according to the rate of
exchange needed, and how controlled the exchange must b
What are the three types of capillaries?
Continuous capillaries (the most widespread) Fenestrated capillaries (leaky). Sinusoidal capillaries (very leaky).
What structures make up a continuous capillary?
Basement membrane
Endothelial layer (tunica intima)
Intercellular cleft
What feature does fenestrated capillaries have?
Fenestrations
What features does Sinusoidal capillaries have?
Incomplete basement membrane
intercellular gap
What is the lymph vascular system?
An open entry drainage system
What are the functions of the lymph vascular system?
Drains excess tissue fluid & plasma proteins from tissues and returns them the blood..
Filters foreign material from lymph
Screens lymph for foreign antigens & responds by releasing antibodies & activated immune cells.
Absorbs fat from intestine and transports to blood.
Describe the structure of the lymphatic system ?
Lymphatic vessels.
Commence as large, blind ending capillaries
From small intestine, a special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli
Larger (thin wall) collecting vessels have numerous valves to prevent backflow.
List the regional lymph nodes?
Cervical nodes
Axillary nodes
Inguinal nodes
What does the structure of lymph nodes consist of?
Afferent lymph vessel
Efferent lymph vessel
Valves control direction of flow
What are the functions of continuous capillaries?
Diffusion through membrane of lipid soluble substances.
Movement through intercellular clefts of water soluble substances.
Transport of large substances via vesicles or caveolae
What are the functions of fenestrated capillaries?
Same as continuous plus the option of movement through fenestrations
What are the functions of sinusoidal capillaries?
Same as continuous and fenestrated but will find that when moving through physical openings, basement membrane may not be present.
What are fenestrations?
Physical openings in the cytoplasm of endothelial cell
Where does lymph from the left side of the face, body and below diaphragm drain into?
Drained vias Lymph collecting vessels, into the thoracic duct (large lymph capillary) which runs and drains into the left subclavian vein, going back into the blood vascular system.
WHere does lymph from the right side of the face and body above diaphragm drain into?
Right lymphatic duct which then drains into the right subclavian vein, going back into the blood vascular system
What does the portal vein do?
Drains blood from the GI tract where it has been gaining nutrients, to the liver where the blood will be filtered
