Circulatory System

Question 1

The functions of the blood.

Answer 1

• Transport of oxygen, nutrients, proteins, heat, and hormones
• Homeostasis (removes waste products and maintains water balance)
• Immune response (clotting blood, defence against infections and pathogens)

Question 2

The components of the blood and the individual functions of each.

Answer 2

RBCs (erythrocytes):
- Transport of oxygen and carbon dioxide
- Has haemoglobin that reacts with oxygen to make oxyhaemoglobin which turns back to haemoglobin when oxygen diffuses in capillaries
- Has bioncave shape to increase surface area

White blood cells:
- Responsible for the body’s immune response and defending it from diseases and pathogens

Phagocytes:
- Same response for all pathogens
- Engulf foreign matter label by marker proteins (opsonins) or attacked by antibodies
- Break them down with enzymes

Lymphocytes:
- Generate specific immune responses
- Made in bone marrow and found in lymph glands

B lymphocytes:
- Stimulated by foreign matter
- Produce many daughter cells that secrete antibodies that attach to antigens

T lymphocytes:
- Categorized by killer and helper T cells

Killer T cells:
- Attack cells infected by viruses to prevent them from spreading

Helper T cells:
- Help killer T cells and B cells multiply by exposing them to foreign matter

Platelets:
- Cell fragments that clot wounds
- Platelets releases enzymes to help turn fibrinogen into fibrin
- Final reaction turns it from soluble to insoluble
- This forms network of fibrin to trap blood cells

Plasma:
- Liquid part of blood
- Carries water, salts, enzymes, nutrients, hormones, and proteins

Question 3

The organization of the cardiovascular system and the flow of blood around it.

Answer 3

• Double circulatory system where blood goes through blood twice in one cycle
• Pulmonary circulation (heart to lungs) and systemic circulation (heart to body)
• Blood flows through arteries to a particular tissue which then narrows down into capillaries where materials are exchanged
• Blood flows through capillaries which then merge into veins that get thicker until it reach the heart

1) Heart pumps blood to lungs to be oxygenated
2) Oxygenated blood is brought back to heart to be pumped to rest of body
3) Blood goes to tissues to exchange materials
4) Blood goes back to heart
to be oxygenated again
5) Cycle repeats

Lungs: pulmonary artery & vein
Heart: Inferior vena cava & aorta
Liver: hepatic artery and portal vein & hepatic vein
Kidneys: Renal artery and vein
Gut: mesenteric artery and hepatic portal vein
Brain: cartoid artery and jugular vein
Lower body: illiac artery and vein

Question 4

The exchange of gases and materials at the lungs and the tissues.

Answer 4

Lungs:
- Takes place in capillaries surrounding alveoli
- Oxygen diffuses into bloodstream to oxygenate blood

Tissues:
- Takes place in capillaries
- Oyxgen diffuses
- Oxygen and nutrients are recived
- Waste products released including carbon dioxide, urea, ammonia

Question 5

The structure of the heart.

Answer 5

• Made of atrium (upper) and ventricles (lower)
• Each are separated by right and left by the septum
• Right side of the heart is for pumping deoxygenated blood and has vena cava and pulmonary artery
• Left side of the heart pumps oxygenated blood and has pulmonary vein and aorta
• Heart also has valves to keep blood flowing in right direction
• Mitral/triscupid valve (left side) and biscupid valve (right side) between atrium and ventricles
• Semi-lunar valves found between ventricles and pulmonary artery or aorta

1) Blood enters atrium through vena cava and pulmonary vein
2) Atrium pumps blood into ventricles
3) Atrioventricular valves close
4) Ventricles contract
5) Semi-lunar valves open and allow blood to flow through aorta and pulmonary artery

Question 6

The blood supply to the heart.

Answer 6

• Coronary arteries on the outside of the heart that supply its muscles with oxygen and nutrients

Question 7

The control of the heart rate.

Answer 7

• Heart rate is controlled by patch of muscles in the right atrium called the pacemaker or sinoatrial node (SAN)
• Sends electrical signals to walls of heart at regular intervals, causing them to contract
• Pacemaker’s rate changes according to body’s needs through sensing pH levels
• Increase in carbon dioxide levels decrease pH levels which is sensed by the receptor cells in the brain, causing it to increase frequency of nerve impulses sent to pacemaker through the Autonomic Nervous System (ANS)

Question 8

The structure and function of the different types of blood vessels.

Answer 8

Arteries:
- Carries blood from heart to body to supply them with oxygen and nutrients
- Thick, muscular walls to resist pulsing of heart
- Elastic walls to contract and relax with pace of pulse to ensure smooth blood flow
- Small lumen to maintain blood pressure

Veins:
- Return blood from body to heart for it to be oxygenated again
- Smaller muscles as blood pressure is lost and there is no need for muscular walls
- Wide lumen to compensate for lack of blood pressure and offer easy blood flow
- Valves to prevent backflow due to lack of blood pressure

Capillaries:
- Supply all cells with nutrients and oxygen and carry away and waste products
- Very thin walls that are one cell thick as pressure is lost and there is no need for thick walls
- Thin walls and narrow lumen bring blood in close contact with the tissue to allow products to diffuse in and out

Question 9

What are HIV and AIDS.

Answer 9

AIDS:
- Condition where body becomes vulnerable to certain infections
- Infections tend to be opportunistic as they take advantage of person’s hindered immune system

HIV:
- Stands for Human Immune Virus
- Known as the cause of AIDs
- A retrovirus, meaning it is made of RNA surrounded by a coat of protein and lipid. When it infects a cell, it makes a DNA copy of itself which becomes incorporated into the host cell, making it harder to detect
- At a certain point in the life cycle, DNA copy of the virus will make many copies of itself, which leave the cell into the blood to infect other cells

Question 10

How HIV reduces the efficiency of the immune system.

Answer 10

• Mainly infects helper T lymphocytes which causes their premature deaths
• Uncertain if caused by virus or killer T lympocytes eliminating infected cells
• Observed that non-infected helper T lymphocytes have defects in functioning
• Hindered immune system allows for opportunistic diseases to attack the body

Question 11

Opportunistic infectious diseases and types of cancer associated with AIDS

Answer 11

• Pneuocystis pneumonia caused by a protozoan attacking the lungs
• Cryptosporidosis caused by protozoan attacking intestines causing diarrhoea and weight loss
• Cryptococcal meningitis caused by yeast-like fungi that affect the brain, causing confusion, fever, and headaches

Question 12

Transmission of the HIV virus.

Answer 12

Sexually: homosexually or heterosexually, from infected semen or vaginal fluids entering the blood of the victim

Blood transfusions: through infected blood or blood products or contaminated needles used by drug users

Infected mothers: can pass HIV to child through pregnancy or breastfeeding

Question 13

Immune Response:

Answer 13

1) Phagocyte engulfs a bacteria
2) Part of the bacteria（antigen) goes to the surface of the phagocyte
3) Phagocyte presents antigen to helper T cel
4) Helper T cell is activated
5) Help B lympocytes and Killer T lymphocytes proliferate
6) Killer T cells kill virus infected cells while B cells produce antibodies to destroy antigens