Capillaires and Lymphatics Flashcards
What is the function of capillaries?
Exchanging nutrients going in, waste going out between blood and tissue
What does the function of capillaries demand?
Very thin walls - passive process allow shorter distances
Large total cross sectional area of capillary bed - rate of exchange dependent on surface area
Slow and smooth blood flow - we don’t want pulsatile flow
What does the longitudinal section of a capillary show?
Runs through fat storage area, know it’s a capillary as can see red blood cells travelling single file down a narrow capillary. Nucleus of epithelial cell forms walls of capillary (found at either end), epithelial cell wrapped around cell forming junctions of itself
What is the intercellular junction?
Short distance between wall of cell and RBC allowing for passive transport of oxygen
Intercellular junction of capillary are tight junctions which form seals between two things, lots of tight junctions means not much can pass through
What are precapillary sphincters?
Precapillary sphincters are composed of smooth muscle cells and can constrict and stop blood running into side branches so blood must go through the vascular shunt from the terminal arteriole straight into the postcapillary venule, moving blood away from exchange surfaces
What is the structure of capillaries and what are the three types?
Structure changes depending on the type of exchange we need
Continuous : most common, found in cardiac muscle, surrounding skeletal muscle, epithelial cell is a continuous barrier between blood and tissue
Fenestrated: create pore openings meaning things don’t have to pass through cytoplasm of epithelial cell
Sinusoidal: openings larger, not very common
What is a continuous capillary?
Lumen diameter of 8-10 micrometers e.g. Skeletal and cardiac muscle
Basal membrane: extracellular matrix, basal lamina, runs around as a connective tissue layer forming continuous connective tissue layer over basal lamina
What is a fenestrated capillary?
Red blood cells travel in single file, continuous basal membrane however has physical pores allowing exchange directly through pore rather than through the cell, allows things that are small enough to pass through - things in solution, not blood cells
E.g. kidney, small intestine
Sinsusoidal capillary?
Can fit three red blood cells, lumen is much larger than other capillaries, not involved with gas exchange, red and white blood cells still can’t escape from these (blood doesn’t haemorrhage) basal membrane is not a continuous layer - incomplete, cells can be seen - liver cells which have nutrient rich plasma
What are the three processes of continuous capillaries?
- Diffusion through membrane
- Movement through intercellular clefts
- Transport via vesicles or caveolae
What are the four processes for fenestrated and sinusoidal capillaries?
- Diffusion through membrane
- Movement through intercellular clefts
- Movement through fenestrations
- Transport via vesicles or caveolae
What are lymphatic channels?
Lymphatic channels are vessels that drain fluid that has left vessel space, drain back and rejoin at right side of heart
What are the functions of lymph vascular system?
Drains excess tissue fluid and plasma proteins from tissues and returns them the blood
Filters foreign material from the lymph
Screens lymph for foreign antigens and responds by releasing antibodies and activated immune cells
Absorbs fat from intestine and transports to blood
Lymphatic system structure
Lymphatic vessels are blind ended (finger like projections) called lacteals in the intestine which pick up fat-laden lymph and drain back into a collecting vessel called the cisterna chyli. Larger collecting vessels have lots of valves to prevent back flow - very thin walls
How are lymph channels different from veins and arteries?
Lymph have thin walls, no red blood cells, carry lymphatic fluid under very low pressure, numerous valves
