Chapter 8 Transport In Mammals - Lecture Notes

Chapter 8: Transport in Mammals Syllabus Objectives: (a) Identify the main blood vessels to and from the heart, lungs, liver and kidney (b) State the functions of blood

1• red blood cells - haemoglobin and oxygen transport 2• white blood cells - phagocytosis, antibody formation and tissue 2

rejection

1• platelets - fibrinogen to fibrin, causing clotting 2• plasma - transport of blood cells, ions, soluble food substances, hormones, carbon dioxide, urea, vitamins, plasma proteins

(c) List the different ABO blood groups and all possible combinations for the donor and recipient in blood transfusions (d) Relate the structure of arteries, veins and capillaries to their functions (e) Describe the transfer of materials between capillaries and tissue fluid (f) Describe the structure and function of the heart in terms of muscular contraction and the working of valves (g) Outline the cardiac cycle in terms of what happens during systole and diastole (Histology of the heart muscle, names of nerves and transmitter substances are not required) (h) Describe coronary heart disease in terms of the occlusion of coronary arteries and list the possible causes, such as diet, stress and smoking, stating the possible preventative measures

8.1 •

Transport in living organisms

How do useful materials reach all body cells / waste from the cells are removed rapidly? Either by

Simple Organisms - Simple Diffusion • Body cells are close to their surroundings.

Complex Organisms – Diffusion is NOT effective as cells are far away from body surface Need a transport system  Circulatory system in mammals, for example

8.1.1Features of a circulatory system Made up of

A circulating fluid to carry materials

A pumping device to drive fluid around body

A system of branched tubes/ vessels connected to the heart through which fluid can circulate and reach 1 all body cells

Blood

8.2 • • •

Heart

Blood

Definition: A fluid tissue Average human adult has about 5.5 litres of blood Composition of blood: Blood Made up of

Blood cells

Plasma

Platelets

•

Pale yellow liquid • 90% water • Carry dissolved substances Function: • Transport of dissolved substances

• • • • • •

White Blood Cells (WBC) Colourless Contains a nucleus Can move about and change its shape Lives for only a few days

Red Blood Cells (RBC) • Biconcave, • • • •

Function: • Protective • Clotting of blood

flattened discs No nucleus Contain haemoglobin Life-span: 3-4 months Formed in bone marrow Function:in Destroyed • Transport spleen and liver of Oxygen

Phagocytes • Produced in • Produced in lymph glands bone marrow and lymph nodes Transport of oxygen (RBC) 8.2.1

•

•

Lymphocytes

Cell fragments Formed in bone marrow

Protective FunctionsAir sac in lung Haemoglobin + Oxygen (Purplish red)

8.2.2

Body cells

Oxyhaemoglobin (Bright red)

Protective functions of blood (WBC+platelets+some plasma proteins) Protective functions

Phagocytosis

Antibody production

Clotting of blood

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Phagocytes engulf and digest foreign particles (eg. Bacteria that enter blood)

Lymphocytes produce antibodies (proteins)

Bacteria clumps undergo

8.2.3 • •

•

Antibodies cause bacteria to clump together (agglutination)

Platelets + damaged cells Ca2+ + Vit. K + thrombin

Antibodies kill bacteria

Antitoxins neutralize toxins produced by bacteria

Fibrinogen  fibrin threads network

(Soluble in plasma)

(Insoluble)

+ trapped RBC

Forms blood clot

Blood Groups

Surfaces of RBC contains antigens, which are the same in all your RBCs Natural antibodies do not react with the antigens on your RBC o However, it could react with antigens from another person o When this happens, the antibodies will cause the RBC to clump together (agglutination) – See Sect 8.2.2 above. o Clumping of RBC leads to the blockage or small blood vessels  prevent smooth flow of blood  death Your blood group is based on the types of antigens and antibodies present in your blood

Blood Group Antigen on RBC Antibody in plasma A Antigen A Antibody b B Antigen B Antibody a AB Antigens A and B No antibodies O No Antigen Antibodies a and b Note: Whenever • Antibody a reacts with antigen A  clumping occurs • Antibody b reacts with antigen B  clumping occurs • No antibody reacting with antigen, or vice versa  no clumping occurs

Recipient Antibody in A (antigen A) blood recipient’s group plasma

Donor’s blood group B (antigen B) AB (antigens A & B)

O (no antigens: universal donor)

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A B AB (universal acceptor) O

b a No antibodies

+ -

+ -

+ + -

-

a and b

+

+

+

-

Legend : +  agglutination (clumping happens) (not compatible) -  no agglutination (no clumping) (compatible)

8.3 • •

Blood Circulation in humans

Mammals possess a double circulation In double circulation, blood passes through the heart twice before it completes one circuit of the body

Low-pressure circulation

Legend A: Atrium V: Ventricle

Median septum High-pressure circulation

Body parts other than lungs

8.3.1

Pulmonary circulation/circuit • •

Carries deoxygenated blood (low oxygen conc) from heart to lungs at low pressure (flows slowly)  Gives blood time to be well oxygenated Blood then becomes oxygenated (high oxygen conc)

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•

8.3.2

Systemic circulation/circuit • •

•

8.4

Oxygenated blood then returns to the heart (to Left Atrium)

Distributes oxygenated blood from heart to all parts of the body except the lungs Then returns the deoxygenated blood from these parts to the heart again Blood leaves heart at high pressure  so that it can reach all the body tissues at a faster rate, bringing oxygen to them rapidly

The Heart

Bicuspid valves Semi lunar valves

Ensures blood flows in one direction

Tricuspid valves • • • •

•

A muscular organ Contracts and relaxes regularly throughout life Consists of 4 chambers  2 atria (upper chambers) (LA & RA)  2 ventricles (lower chambers) (LV and RV) Median septum separates LA & LV from RA & RV  Prevents mixing of oxygenated blood on left side of heart with deoxygenated blood on right side  Ensures • All oxygenated blood is sent to all parts of body • All deoxygenated blood goes to the lungs Structure of atria and ventricles Chamber Structure Adaptation

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• •

Atria Walls are thin Only needs to force blood into ventricles Ventricles Walls are thick Needs to push blood out of the heart Walls of LV is thicker than RV  enables it to pump blood more forcefully at high pressure to the rest of the body Presence of valves to prevent backflow of blood  ensure that blood flows in one direction only

8.4.1Mode of action of the heart Blood fills atria from veins

Atria contracts

Atria relax

Semi lunar valves close  “dub” sound Ventricles relax

Atria begin to relax

Tricuspid/Bicuspid valves open Blood enters relaxed ventricle

Ventricle contracts

Tricuspid/Bicuspid valves close  “lub” sound Blood pumped into arteries

Semi lunar valves open

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Ventricle relaxing •

•

Ventricle contracting

1 heart-beat = 1 contraction (systole) + 1 relaxation (diastole) of atria & ventricles As ventricles contract  arteries dilate o Each dilation cause elastic walls of arteries to recoil  force blood along as a series of waves/pulses o This pulse rate is  High after exertion  Low during rest

8.5

Blood vessels Blood vessels

Arteries

Carry blood away from heart

Capillaries

Take nutrients, oxygen and useful substances to the cells and remove waste produced in cells

Veins

Carry blood towards heart

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8.5.1 Comparison between blood vessels Blood vessel Wall and Lumen

Artery Wall is thick, muscular and elastic

Capillary Wall is one-cell thick, lumen size of a RBC

Vein Wall is thin, less muscular and elastic

Diagram of cross-section

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Valves

Absent

Absent

Blood flow

1. Blood moves along by contraction of the muscles of its walls.

1. Blood flows smoothly

2. Blood flows under great pressure, fast, in spurts. Nature of blood

Oxygenated (except for pulmonary artery)

Semi-lunar valves to prevent backflow of blood 1. Blood flows smoothly and slowly

2. Pressure at arteriole end > pressure at venule end.

Oxygenated at arteriole end, deoxygenated at venule end (except lungs!)

2. Blood moves along vein by contractions of the body muscles on the vein Deoxygenated (except for pulmonary vein)

8.5.2 Coronary arteries • •

2 Coronary arteries supply the heart muscles with nutrients and oxygen Coronary heart disease (CHD)

Fat deposits (atherosclerosis)

Blood clots (thrombosis)

Heart muscles do not get enough nutrients/oxygen

Partially block the lumen of coronary arteries

Heart muscles start to degenerate

Obstruct blood flow to the heart muscles

Severe heart pain  9 heart attack

•

8.6

Causes of CHD: High fat diet, smoking, being overweight, lack of exercise, stress

Transfer of materials between capillaries, tissue fluids and body cells •

Body cells are bathed in tissue fluid o Tissue fluid = dilute plasma without plasma proteins

Some enters tissue fluid

•

Role of tissue fluid: o To allow nutrients and oxygen to diffuse out of the blood in capillaries into the fluid, and then eventually to body cells o Waste products formed by the cells diffuse out of the tissue fluid, and from there diffuse into the blood in the capillaries

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