Animal Transport Systems

• Transport in animals occurs through the circulatory and lymphatic systems.

Circulatory System

• Consists of blood, blood vessels, and the heart.
• It is a system of tubes with a pump (the heart) and valves to ensure one-way blood flow.

Blood

• About 6 liters in volume.
• Slightly alkaline with a pH of 7.4.
• Consists of red blood cells, white blood cells, platelets, and plasma.
• Plasma makes up 55% of blood, while red blood cells constitute 45%.

Blood Components

• Plasma: Pale yellowish liquid, mainly water (90%), containing dissolved substances like proteins, ions, nutrients, and wastes.
• Red Blood Cells (Erythrocytes): Transport oxygen and a small amount of carbon dioxide. Formed in bone marrow, contain hemoglobin, which binds to oxygen forming oxyhemoglobin. Old red blood cells are broken down in the liver, spleen, and bone marrow.

Adaptations of Red Blood Cells

• Very small to pass through fine capillaries.
• Have elastic walls for squeezing through capillaries.
• Contain haemoglobin to transport oxygen.
• Biconcave shape to increase surface area for oxygen combination.
• No nucleus to maximize space for haemoglobin and oxygen transport.
• Produced at a high rate due to a short lifespan (~120 days).

White Blood Cells (Leukocytes)

• Protect against microbes (pathogens or germs). Formed in bone marrow.
• Two Types:
• Phagocytes: Engulf foreign bodies such as bacteria, microbes, or germs and secrete enzymes to digest them.
• Lymphocytes: Produce antibodies (proteins) that attack microbes, germs, or pathogens, and make germs easier to engulf.

Platelets (Thrombocytes)

• Necessary for blood clotting.
• Fragments formed from special cells in the bone marrow.

Blood Plasma

• Fluid in which blood cells and platelets move.
• Transports urea, hormones, digested food, antibodies, water, and salts.
• Composed of water, ions (sodium, potassium, calcium, chloride), and plasma proteins (fibrinogen, globulin, formed in the liver).

Blood Clotting

• When skin is wounded, clotting factors are released by damaged cells and platelets.
• Platelets become sticky and adhere to the damaged region to form a plug.
• Prothrombin converts to thrombin, which catalyses the conversion of soluble Fibrinogen into insoluble fibrous fibrin.
• Fibrin forms a mesh around the wound, trapping blood cells to form a temporary clot (scab).

Importance of Blood Clotting

• Protects against bleeding and prevents pathogens from entering wounds.

Blood Vessels

• Arteries carry blood from the heart, veins carry blood to the heart, and capillaries connect arteries and veins.

Arteries

• Carry blood from the heart to the body.
• Narrow lumen, thick walls, high pressure, with rapid irregular flow.
• Small arteries are called arterioles.
• They are adapted with thick walls to withstand high blood pressure, elastic walls to aid blood propulsion, and embedding in muscles for protection due to healing difficulties under high pressure.

Veins

• Carry blood from the body to the heart.
• Wider lumen, thinner walls, lower pressure, and slow regular flow.
• The smallest veins are called venules.
• Body muscles help blood to be squeezed in veins

Adaptation of Veins

• Wide lumen for less resistance.
• Thinner walls and lower pressure than arteries.
• Slow, regular flow of blood.
• Smallest veins are called venules.
• Body muscles help blood.
• Contain valves to prevent backflow.

Capillaries

• Very fine vessels with one-cell-thick walls that connect arteries and veins.
• Have fine gaps in cell walls for exchange of materials with surrounding body cells.
• Large in number to increase surface area for material exchange between blood and body tissues.

Shunt Vessels

• Link arterioles directly to veins or venules, allowing blood to bypass the capillaries.
• Can control blood flow via constriction and dilation.

Arteries, Veins and Capillaries

• Arteries carry blood from heart to rest of body, carry mostly oxygenated blood, have high pressure with thicker walls, and no valves
• Veins carry blood from rest of body to heart, carry mostly deoxygenated blood, have low pressure with thinner walls, and have valves
• Capillaries connect arteries to veins, carry both [de]oxygenated blood, have walls only one-cell thick for diffusion, and no valves

Heart Valves

• Bicuspid and tricuspid valves described as atrio-ventricular, since they are found between atria and ventricles
• Right atrium and right ventricles separated by the tricuspid valve (3 flaps).
• Left atrium and left ventricle are separated by the bicuspid or mitral valve (2 flaps).

Heart Valves Function

• Prevent back flow of blood, and allow blood flow in one direction. Blood coming from atria forces them to open.
• Tendons prevent them from being turned back towards atria

Semilunar Valves

• Flaps act as pockets, and when blood tries to flow back they fill with blood and close.

Blood Flow through Heart

• Superior vena cava collects deoxygenated blood from upper parts, and Inferior vena cava collects deoxygenated blood from lower parts, both to the right atrium.
• The heart muscle is supplied by coronary arteries which branch from the aorta

Types of Circulation

• Pulmonary circulation flows from the right ventricle to the lungs, then back to the left atrium.
• Systemic circulation flows from the left ventricle and ends in the right atrium.

Characteristics of Circulation in Humans

• It is a closed circulatory system.
• It is a double (or dual circulatory system).

Advantages of Double Circulation

• Higher blood pressure can flow so higher flow rate than in singular circulation.
• Prevents mixing of oxygenated and deoxygenated blood.
• Allows animals to have high metabolic rates.
• Allows animals to be large and tall.

Single Circulation

• Blood passes through heart once in one complete circuit to body.
• A lot of pressure is lost during flow of blood making flow of blood in the body very slow decreasing the supply of oxygen to the body.

Blood Pressure

• Pressure created in arteries due to flow of blood during heart beats.
• It is measured with a sphygmomanometer. Normal is 120/80 mm/Hg.
• 120 is systolic pressure, the pressure during ventricular contraction.
• 80 is diastolic pressure, blood pressure during ventricular relaxation.

Heart Sounds

• They are produced by heart valves.
• "Lub" is caused by closing valves leading to the ventricles.
• "Dub" is caused by closing valves leading out of the heart.

Pulse

• The ripple of pressure passing down an artery due to heartbeats is the pulse.
• The rate of pulse represents the rate of heartbeats.

Heart Rate Factors

• It decreases during sleeping or relaxation.
• It goes over 100 / min during exercise.
• Factors such as adrenaline or caffeine consumption increase heart rate, while sleep decreases it.

Electrocardiogram (ECG)

• P = Atrial Systole (wave of excitation in atria).
• Q, R, S = Ventricular Systole (wave of excitation in ventricles).
• T = Atrial and Ventricular diastole (recovery of the ventricle walls).

Heart Attack Causes

• Coronary arteries becomes blocked causing the heart muscle to be starved due to the lack of food and oxygen.

Atherosclerosis Main Causes

• Too much animal fats which precipitate on the inner walls of arteries leading to reduction in their lumen and elasticity
• Too much salts increases blood pressure
• Smoking and stress
• Age and genetic factors