Transport in Humans Flashcards
Describe the structure of arteries and their purpose
- The walls of arteries are very thick (muscle-outer layer- and elastic tissue-inner layer) and are able to push incoming blood by distending and rebounding along the length
- Arteries have relatively small lumens to keep blood pressure above a critical value
Why do arteries need thick walls?
To withstand the high blood pressure as well as to maintain the pressure
What is the function of arteries?
Blood vessels that carry blood away from the heart to the rest of the body
Describe the structure of veins
- Relatively thin walls
- Larger lumen than arteries
- Have semi-lunar valves to prevent backflow of blood
What is the function of the vein
Blood vessels that carry blood towards the heart from the rest of the body
Describe the structure of capiliaries
- Walls are one cell thick
What is the innermost layer of arteries and veins called?
Endothelium
What is the function of capiliaries?
Connect arteries to veins. Site of exchange of substances
Compare blood plasma and tissue fluid
Tissue fluid is plasma without plasma proteins and RBCs. Plasma in the blood vessels, tissue fluid when outside of blood vessels in intercellular spaces
What is oedema?
When more tissue fluid forms than can be drained, and accumulates in tissue and causes it to swell. The increased water acts as a cushion
What is the function of tissue fluids?
2 functions
- Hydrates tissues and cells
- Medium for diffusion of nutrients and respiratory substrates, as well as waste materials in the reverse direction
What are the components of blood?
4 components
- Plasma (liquid part of the blood; made in the liver)
- Platelets (cell fragments; for maintainance of blood volume and thus pressure)
- Red blood cells
- White blood cells
What are the events following tissue damage?
- Platelets gather at the damaged site
- The platelets as well as damaged tissues release thrombokinase which catalyses the inactive prothrombin to active thrombin
- Thrombin catalyses the inactive fibrinogen to the active fibrin
- Fibrin takes on the form of insoluble fibrin threads
- These threads entrap mainly RBCs ath the site to form a hardened mass
- Platelets also assist in plugging up the site physically
This prevents excessive loss of blood and reduces entry of pathogens into the bloodstream
Describe the transport of oxygen around the body by red blood cells
- At the lungs, oxygen molecules bind reversibly to haemoglobin in the RBC to form the unstable oxyhaemoglobin and is transported around the body
- At oxygen-poor sites, oxygen is released and leaves the haemoglobin free to pick up more oxygen at the lungs again
Describe the transport of carbon dioxide around the body
- Very little CO2 is transported in the dissolved form
- Most are transported as hydrogen carbonate ions in blood plasma instead
1. Carbon dioxide + water —-carbonic anhydrase—-> carbonic acid
2. Carbonic acid dissociates to release hydrogen carbonate ions and hydrogen ions
The process is reversed when the blood reaches the lungs
Note: carbonic anhydrase is found in RBCs
What are the two types of white blood cells?
- Lympocytes
- Phagocytes
What is the structure and function of lymphocytes?
1 structure, 2 function
Structure
1. Round shaped with large bean shaped nucleus
Function
1. Synthesise and secrete antibodies in response to foreign body invasion and act as memory cells for future infections (B-cells)
2. T cells directly attack the pathogens by creating holes in their cell membrane and adding enzymes
What is the structure and function of phagocytes?
Structure
1. Larger cells with multi-lobed nucleus
2. Cytoplasm has a granular appearance
3. No defined shape
4. Can move by cytoplasmic streaming
5. Able to squeeze through gaps in the cells of the capiliary wall and crawl to sites of infection amongst tissues
Function
1. Engage in phagocytosis; engulf and digest pathogens using intercellular enzymes
2. Also ingest cell debris and worn out cell
5 structure, 2 functions
What are the antibodies present in each blood type?
A: anti-b
B: anti-a
AB: none
O: anti-a and anti-b
What are the antigens present on each blood type?
A: Antigen A
B: Antigen B
AB: Antigen A and B
O: None
What happens when non-compatible blood types are transfused?
Blood agglutination occurs when the antibodies in the blood detect a foreign antigen, causing it to attach to the foreign cell and cause clumping of those cells
What are the chambers of the heart and what type of blood do they pump?
- Left atrium, oxygenated
- Left ventricle, oxygenated
- Right atrium, deoxygenated
- Right ventricle, deoxygenated
What are the various vesssels that carry blood in and out of the heart and from/to where?
- Vena cava (body to right atrium)
- Aorta (left ventricle to body)
- Pulmonary vein (lungs to left ventricle)
- Pulmonary artery (right ventricle to lungs)
What are the various valves in the heart?
- Tricuspid valve (right ventricle)
- Bicuspid valve (left ventricle)
- Semi-lunar valves (before aorta and pulmonary artery)
