Lecture 7: Capillaries and Lymphatics Flashcards
What is the function of Capillaries?
Site of exchange between blood and tissues
What does the large total area of the capillary bed compared to arterioles mean?
Much slower blood flow
What are 3 features of capillaries?
- Very thin walls
- Large total cross sectional area of capillary bed
- Slow & smooth blood flow
What are erythrocytes?
Red blood cells
Why are Capillaries only approximately 1 red blood cell in width?
Reduces the distance from the red blood cell to the surrounding tissue
What type of intercellular junction fuses the Capillary cell shut?
Tight junctions
What drains into Capillary beds?
Arterioles
What drains from the Capillary beds?
Venules
What is the role of the Precapillary sphincters?
Constrict to stop blood going into the Capillary beds
What is the name of the pathway that allows blood from the arteriole to the venules without passing through the exchange surface?
The Vascular shunt
Why is blood shunted away from the capillary beds?
To stop heat loss from blood and keep it away from the skin surface
What are Precapillary sphincters composed of?
Smooth muscle cells
What are the 3 types of Capillaries?
- Continuous
- Fenestrated
- Sinusoidal
What components make up a Capillary?
3
- Basement membrane
- Endothelial layer
- Intercellular cleft
What produces the Basement membrane?
The endothelial cell of the Capillary
What do substances have to pass through from the Capillaries to go to the tissue?
Both the Endothelial cell and the basement membrane
What is an intercellular cleft?
A channel between two cells through which molecules may travel
What do vesicles in the Capillaries do?
They carry things that can’t move by passive diffusion
Where are continuous Capillaries likely to be found?
Skeletal and Cardiac muscle
What are the openings in fenestrated capillaries?
Small porous openings/physical openings
What is the approximate size of Continious/Fenestrated capillaries?
8-10 microns in diameter
Why is the lumen bigger in Sinusoidal Capillaries?
Trying to facilitate exchange with something other than gases
What is an example of where Sinusoidal Capillaries are found?
Liver
What happens to the basement membrane around sinusoidal capillaries?
It is disrupted and cannot be seen
How is permeability controlled at intercellular clefts?
By the amount of tight junctions that are present there
What are 4 ways of transport from Capillaries?
- Diffusion through membrane
- Movement through intercellular clefts
- Movement through fenestrations
- Transport via vesicles
What Type of substance move by diffusion through membranes?
Lipid-soluble substances
What Type of substance move by movement through intercellular clefts/fenestrations?
Water soluble substances
What Type of substance move by transport via vesicles?
Large substances
What type of movement across the membrane occurs through Fenestrated/Sinusoidal Capillaries?
All types of movement
What type of movement doesn’t occur at Continuous Capillaries?
Movement through Fenestrations
How is fluid shifted back to the heart that has left the blood vascular system?
Lymph Vascular system
What is the role of lymph nodes in the lymph system?
Immune system surveillance
What are the functions of the Lymph Vascular system?
4
- Drain excess tissue fluid/plasma proteins and return to the blood
- Filter foreign material from the lymph
- ‘Screens’ lymph for foreign antigens and responds by releasing antibodies
- Absorbs fat
What are lacteals?
Special lymphatic cells that drain fat
Where is fat from the gut drained too?
Cisterna chyli
What is present all throughout the lymph vessels?
Valves
What is particular about Lymph channel walls?
They are the thinnest walls of all vessels
What are 3 features of lymph vessels?
- Thin walled
- No Red blood cells
- Possess valves
What is the left side of the body any everything below the diaphragm drained through?
The Lymphatic collecting vessels
What do the Lymphatic collecting vessels drain into?
The Thoracic duct
What is the only type of fluid found at in the Thoracic duct?
Lymphatic fluid
What does the Thoracic duct drain into?
The left Subclavian Vein
What does the right side of the face/right upper limb and right side of the chest drain through?
Right lymphatic duct
What does the right lymphatic duct drain through?
The right Subclavian vein
What carries blood with nutrients from the intestines to the gut?
The Portal vein
What is a Lacteal?
A special lymph capillary for draining fat
Where are typical places for lymph nodes to be clustered?
3
- Armpit
- Groin
- Neck
What does lymph fluid pass into the lymph node through?
Afferent lymphatics
What does lymph fluid pass out of the lymph node through?
Efferent lymphatics
In order what is the drainage path of the right breast?
4
- Lymphatic vessels of the breast
- Axillary lymph node
- Drained into the right lymphatic duct
- Right Subclavian vein (Blood vascular system)
