ch5 circulatory system Flashcards
Define:
Circulatory system
The link between the cells inside the body, which have certain requirements, and the environment outside the body, which supplies those requirements.
Blood functions
- Transporting oxygen and nutrients to all cells of the body
- Transporting carbon dioxide and other waste products away from the cells
- Transporting chemical messengers, called hormones, to the cells
- Maintaining the pH of body fluids
- Distributing heat and maintaining body temperature
- Maintaining water content and ion concentration of the body fluids
- Protecting against disease-causing micro-organisms
- Clotting when vessels are damaged, thus preventing blood loss.
Blood components
- Plasma: liquid part, making up ~55% of the blood volume
- Formed elements: non-liquid part ~45% of the blood volume
- Erythrocytes (red blood cells)
- Leucocytes (white blood cells)
- Thrombocytes (platelets)
***** Plasma structure and function
A mixture of liquid and dissolved substances such as sugar and salts.
Transport the components of blood, including
Define:
Erythrocytes (RBC)
State function and abundance
The most abundant cells in the blood, whose purpose is to transport oxygen to cells. Accounts for 40-45% of the blood volume
This percentage is called the haematocrit.
Erythrocytes structure
- Biconcave (flattened in the middle on both sides)
- Don’t contain a nucleus
- Increases flexibility and, hence, their ability to move through blood vessels.
- But, lack of nucleus limits lifespan to around 120 days.
Leucocytes (WBC) function and abundance.
Protect the body from infection. Only 1% of the blood volume.
Types of leucocytes.
- Neutrophils
- Monocytes
- Lymphocytes
- Basophils
- Eosinophils
Neutrophils function
Contain enzymes to digest pathogens
Monocytes function
Form other cells, including macrophages.
Macrophages function
Engulf pathogens and aged/damaged cells through phagocytosis.
Lymphocytes function
State two types
Involved in immune response.
* T-lymphocytes
* B-lymphocytes
T-lymphocytes function
Involved in cell-mediated immunity.
B-lymphocytes function
Involved in antibody-mediated immunity
Basophils function
Involved in allergic reactions — they produce heparin and histamine to defend the body against parasites and bacteria.
Eosinophils function
Lead inflammatory responses — they respond to larger parasites such as worms.
Thrombocytes structure and function
Small fragments of cells. When a blood vessel is injured, they adhere to the lining and form a scaffold for the coagulation of blood to form a clot.
What are the two ways oxygen is transported in the blood?
- 3% is carried in solution in plasma
- 97% is carried in red blood cells as oxyhaemoglobin
How is oxygen transported in red blood cells?
Haemoglobin combines with oxygen to form a compound called oxyhaemoglobin.
This happens when the oxygen concentration is relatively high.
Oxygen concentration is high in the capillaries in the lungs, where oxygen diffuses into the blood from the air in the alveoli.
Oxyhaemoglobin can easily break down to release the oxygen.
This happens when the oxygen concentration of relatively low.
As the cells of the body are continually using oxygen, the tissue fluid around the cells has a relatively low oxygen concentration. Therefore, when red blood cells flow through the capillaries between body cells, they give up their oxygen, which diffuses into the tissue fluid and then into the cells.
What colour is oxygenated blood and why?
Oxyhaemoglobin is bright red, so the blood in the arteries (except the pulmonary arteries taking blood to the lungs) is bright red.
What colour is deoxygenated blood and why?
Haemoglobin is dark red or purplish, so the deoxygenated blood in the veins (except the pulmonary veins from the lungs) is dark red.
Why are red blood cells well suited to transport oxygen?
Structure
01. contain haemoglobin
which is able to combine with oxygen.
02. have no nucleus
so there is more space for haemoglobin molecules.
03. are shaped like biconcave discs
the biconcave centre increases the surface area for oxygen exchange and the thicker edges give a large volume that allows space for the haemoglobin molecules.
What are the three ways carbon dioxide is transported in the blood?
- 7-8% is dissolved in plasma and carried in solution.
- 22% is carried as carbaminohaemoglobin.
- 70% is carried in plasma as bicarbonate ions (HCO₃⁻)
How is carbon dioxide transported between the blood and lungs?
As blood is flowing through the capillaries between body cells, carbon dioxide diffuses into the plasma due to the difference in carbon dioxide concentration (low in plasma, high in body cells).
- Some carbon dioxide dissolves in the plasma
- Some combines with haemoglobin
- Most reacts with water to form carbonic acid (H₂CO₃)
- Carbonic acid then ionises into hydrogen ions and bicarbonate ions
Recall: alveoli are highly vascularised - they are surrounded by a dense network of capillaries.
Carbon dioxide dissolved in the plasma diffuses out of the blood (from capillary) into the air in the alveolus.
→ Hydrogen ions and bicarbonate ions recombine to form carbonic acid.
→ Carbonic acid then breaks down under enzyme actin into water and carbon dioxide.
→ This carbon dioxide also diffuses into the alveolus.
How are nutrients and waste transported in the blood?
In the blood plasma.
Define:
Nutrients
The essential elements and molecules that are obtained from the food we eat.
List:
Inorganic nutrients
- sodium
- calcium
- potassium
- chloride
- iodide
List:
Organic nutrients
- glucose
- vitamins
- amino acids
- fatty acids
- glycerol
Define:
Metabolic wastes
Substances produced by cells that cannot be used and would be harmful if allowed to accumulate.
List:
Metabolic wastes
- urea
- creatinine
- uric acid
Vasoconstriction definition and purpose
during injuries
Muscles in the walls of the small arteries that have been injured or broken constrict immediately.
Purpose: reduce blood flow, and therefore, blood loss.
Platelet plug definition and purpose
Damage creates a rough surface on internal walls of blood vessels to which the platelets can stick. Sticking platelets attracts more platelets, and so a plug is build up at the site of the injury.
Purpose: reduce blood loss.
This plugging and blood vessel constriction is enough to stop any bleeding for very small tears in capillaries.
Platelets also release substances that act as vasoconstrictors.
Purpose: enhance and prolong the constriction of the damaged vessels.
Coagulation (blood clotting) definition and purpose
The series of chemical reactions causes the formation of threads of fibrin: an insoluble protein.
The fibrin threads form a mesh that traps blood cells, platelets, and plasma. This mesh, with its trapped material, is the clot or thrombus. The threads stick to the damaged blood vessels and hold the clot in position.
Purpose: prevent excessive bleeding when a blood cell is injured.
Involves clotting factors present in plasma.
Define:
Heart
The (four-chambered) pump that pushes blood around the body.
Heart location
Between the two lungs in the mediastinum, behind and slightly to the left of the sternum.
Heart shape and size
Conical shape, approximately 12cm long, 9cm at its widest point and 6cm thick.
Heart membrane
Holds the heart in place, but also allows it to move as it beats. It also prevents the heart from overstretching.
Heart wall structure
Made up of cardiac muscle.
Heart septum
The wall that separates the left and right sides of the heart.
Heart right side function
Collects blood from the body and pumps it to the lungs (to get oxygenated).
Heart left side function
Receives blood from the lungs (oxygenated) and pumps it to the rest of the body.
Heart chambers
Each side of the heart is also divided into two chambers — two chambers per side = four chambers.
Atria (single: atrium): top chambers.
Ventricles: bottom chambers.
Atria function
Collect blood from the body and lungs.
Ventricles function
Pump blood out of the heart to the lungs and body.
Right atrium function
Receives blood from the body and passes it to the right ventricle.
Right ventricle function
Pumps blood to the lungs.
Left atrium function
Receives blood from the lungs and passes it to the left ventricle.