Lecture 7 Flashcards
(34 cards)
What is the function of capillaries?
Site of exchange between blood and tissues
What are the functional demands of capillaries?
Thin walls, large cross-sectional area, slow and smooth blood flow
What is the speed of blood flow of capillaries in comparison to arteriole’s?
Slow
What is the basic structure of a capillary?
A tube formed by simple squamous epithelia, surrounded by a basement membrane of extracellular matrix
What feature controls the flow into capillary beds?
Precapillary sphincters
What are the precapillary sphincters composed of?
Smooth muscle cells
What is the function of the precapillary sphincters
To control the flow of blood from the Terminal arteriol to the capillary bed
What vessels supply the capillary beds?
Terminal arterioles
What feature of a capillary bed directs blood straight through the thoroughfare channel?
Vascular shunts
What is the function of vascular shunts?
They direct blood through a large thoroughfare channel, rather than into all the different parts of the capillary bed.
What are the capillary structures?
Continuous, Fenestrated, sinusoidal
What are continuous capillaries?
The most widespread, tightest capillary of 8-10 μm, allows one red blood cell to pass at a time
What is the basement membrane?
thin layers of specialised extracellular matrix that form a supporting structure around the capillary
What are fenestrated capillaries?
A slightly leaky capillary of 8-10 μm, allows one red blood cell to pass at a time and contains small fenestration in which water-soluble molecules can pass. Basement membrane complete
What are sinusoidal capillaries
A leaky capillary of 30-40 μm, allows multiple red blood cells to pass at a time and contains larger fenestration in which water-soluble molecules can pass. Basement membrane incomplete
What are the forms of transport for continuous capillaries?
Diffusion through membrane (Lipid-soluble), movement through intracellular clefts (water-soluble) and transport via vesicles (larger molecules)
What are the forms of transport for fenestrated and sinusoidal capillaries?
Diffusion through membrane (Lipid-soluble), movement through intracellular clefts (water-soluble), movement through fenestrations (water-soluble) and transport via vesicles (larger molecules)
What is the lymph vascular system?
An open-entry drainage system
What are the functions of the lymph vascular system?
Drains excess tissue fluid and plasma proteins from tissues and returns them to the blood. Filters foreign material, ‘screens’ lymph for foreign antigen and responds by releasing antibodies and activated immune cells, absorbs fat from intestine and transports to blood in GI tract
What are lacteals?
A special group of lymphatic vessels from small intestine
What are cisterna chyil
The vessels that lacteals drain fat-laden lymph into
What is a feature of the lymphatic system due to the low-pressure nature of the system?
Larger collecting vessels have numerous valves to prevent backflow
What is a cellular feature for easy drainage in the lymph vascular system?
Simple squamous epithelial cells are loosely packed
What features of a transverse histological section of tissue would distinguish between veins, arteries and lymph channels?
Arteries: Very thick walls, low CSA
Veins: Very thin walls, high CSA
Lymph channel: irregularly shaped thinner walls
