8.2 Blood Vessels, Blood, Tissue Fluid & Lymph Flashcards
What are 3 examples of some of the components used in our blood vessels
- collagen - for structure and support of vessels
- smooth muscle - contracts or relaxes to change lumen shape
- elastic fibres - stretch or recoil for vessel flexibility
What is the structure of the artery
from outer to inner: 1. tough collagen 2. stretchy smooth muscle 3. flexible elastin fibres 4. endothelium lining of artery 5. lumen All to withstand the high pressure of blood passing through arteries/arterioles
What are arterioles and what is their structure
Vessels that link the arteries and capillaries; they have more smooth muscle and less elastin than arteries as they have a little pulse surge, but can still constrict or dilate.
What are capillaries
Tiny vessels that link arterioles to venules; so tiny RBC have to travel single file.
Why is exchange of substances between tissue cells and blood
Because the gaps between the endothelial cells (that make up the capillary wall) are relatively large
Is blood oxygenated when it leaves the venule end
It’s oxygenated going into the capillary from the arteriole but becomes deoxygenated, and full of carbon dioxide as it reaches the venule end.
How are capillaries adapted for their role
- provide large SA for diffusion
- rate of blood falls as the total cross-sectional area of capillaries is always greater than arterioles = more diffusion time
- walls are one endothelial cell thick
Where does deoxygenated blood come from, to enter the veins and venules
From capillaries; capillaries –> venules –> larger veins
What are the 2 vessels that carry dexoy. blood to the heart
Inferior and superior vena cava
Do veins have a pulse
No, the pulse is lost when the blood goes into narrow capillaries
Why do veins have valves but arteries don’t
to prevent backflow of blood as the pressure is lower in veins than arteries
What is the structure of a vein
From outer to inner layers: compared to arteries
- thinner layer of collagen
- thinner layer of muscle
- thinner layer of elastin
- endothelium lining
- wider lumen
What are the 3 main adaption for veins to get blood back to the heart under low pressure
- majority of veins have one way valves at intervals
- many of the bigger veins run through big muscles so when they contract they help to squeeze the blood to the heart
- breathing movements of the chest acts as a pump - the pressure changes moves blood to heart from chest and abdomen
What is the main component of blood
yellow blood plasma
What are the smaller components of blood
dissolved glucose and amino acids, mineral ions, large plasma proteins (albumin - important for maintaining osmotic potential of blood), fibrinogen globulins (important for transport and immune system). platelets RBC WBC
What is the function of the blood
- oxygen to and CO2 from respiring cells
- digested food from small intestine
- waste from cells to excretory cells
- hormone transport
- platelets to wounds
- cells and antibodies involved in the immune system
Also acts as a buffer to minimise pH changes and temp changes
What is oncotic pressure
the tendency for water to move into the blood; it’s about -3.3kPa
Why does water have a tendency to move into the blood
Plasma proteins have an oncotic effect, in which they cause the blood to have a high solute potential, resulting in a low water potential.
What is hydrostatic pressure
As blood flows through the arterioles into the capillaries, it is still under pressure from the surge of blood pumped from the heart. It’s about 4.6kPa
How is tissue fluid formed
the hydrostatic pressure is higher than the oncotic pressure so water is attracted in by osmosis, forcing fluid out of the capillaries. This fluid fills the extracellular space between the cells, called tissue fluid.
Diffusion happens between the blood and the cells through the tissue fluid.
What causes hydrostatic and oncotic pressure to change
the movement of blood from the arteriole end to the venule end.
Hydrostatic decreases to around 2.3kPa but oncotic stays at -3.3kPa so it’s now stronger.
Water now rushes in the capillary towards the venous end. By the time the blood returns to the vein, 90% of the tissue fluid is back in the vessel.
oncotic pressure=-3.3kPa
Arteriole end: Venule end:
4.6kPa HP (high) 2.3kPa HP (low)
4.6-3.3=1.3kPa 2.3-3.3=-1.0kPa
fluid forced out = tissue fluid fluid rushes back in
What happens to the remaining 10% of tissue fluid that doesn’t go back into the capillary
It is drained into the lymphatic system and becomes known as LYMPH
What is different about lymph from tissue fluid and plasma
Has same composition but less oxygen and nutrients; contains fatty acids which have been absorbed from the small intestine.
Where does the lymph fluid join the blood plasma again
After being transported around the body, through larger vessels that have valves to prevent backflow, they enter the left and right SUBCLAVIAN veins (under the clavicle)
What builds up in the lymph nodes around the body
lymphocytes which produce antibodies which go into the blood to be transported around
Why is the lymphatic system important
It intercepts debris and bacteria in the lymph to be ingested by phagocytes found in the nodes so plays a major role in the immune system/defence mechanisms of the body.
What do enlarged lymph nodes indicate
The body is fighting off a pathogen
