Please enable JavaScript.
Coggle requires JavaScript to display documents.
3.2.1 Transport in Animals (Formation of Tissue Fluid (Composition: (Blood…
3.2.1 Transport in Animals
Why do we need a transport system
Size
larger organisms means innermost cells are far away from environment so diffusion pathway increases, and diffusion cannot supply all needs
SA:V
larger animals means smaller surface area to volume ratio
Level of metabolic activity
aerobic respiration requires oxygen, physical movement and activity uses energy through respiration, and mammals need to keep themselves warm, which uses energy
Features of a good transport system
fluid or medium to carry substances such as oxygen, carbon dioxide, nutrients, waste products; the blood
pump to create pressure to push fluid around; the heart
exchange surfaces so substances can enter and leave the blood in the right places; the capillaries
may have tubes or vessels to carry blood by mass flow; arteries and veins
two circuits, one to pick up oxygen, and one to deliver oxygen to tissues; double circulatory system in humans
Single vs Double Circulatory System
Single
blood flows though heart once for each circuit of the body
e.g. in fish: heart -> gills -> body -> heart
blood pressure is always low as it passes through tiny capillaries and rate at which oxygen and nutrients are delivered is limited
Double
blood flows though heart twice for each circuit of the body, once to pick up oxygen, then once to deliver to tissues
e.g. in humans: heart -> body -> heart -> lungs -> heart
heart increases blood pressure after passing through lungs so is at higher pressure flowing through body and flows quicker
Open vs Closed Circulatory System
Open
blood is not held in vessels, so blood fluid circulates around body so tissues and cells are bathed directly in blood e.g. insects
may or may not have a pump (like a heart) to keep blood flowing, blood may circulate due to movement of body
blood pressure is low
blood flow is slow
Closed
blood pressure is high
blood is held in vessels, so blood fluid circulates around body; separate fluid for tissue e.g. humans
blood flow is high
rapid delivery of oxygen and nutrients
transport not limited by body movements
blood is held in vessels, and a separate fluid (tissue fluid) bathes tissues
high blood pressure; blood flow is faster
rapid removal or carbon dioxide and wastes
Blood Vessels
arteries
oxygenated blood away from heart
arterioles
oxygenated blood from arteries from capillaries
capillaries
exchange of materials between blood and tissue fluid
venules
deoxygenated blood from capillaries to veins
veins
deoxygenated blood to heart
Formation of Tissue Fluid
Composition:
Blood: plasma; erythrocytes; neutrophils; lymphocytes; plasma proteins; fats transported in lipoproteins
Lymph: lymphocytes; few proteins; more fats near digestive system
Tissue fluid: surrounds body cells; some neutrophils in infected areas; few proteins and fats
high hydrostatic pressure at arterial end of capillary; blood fluid is pushed out of capillary wall through tiny gaps between cells in capillary wall
hydrostatic pressure: pressure that is exerted by a fluid on the sides of the container holding it; tends to push fluid out of vessels
white and red blood cells, and large proteins remain in blood, as they are too big to fit in the gaps
low hydrostatic pressure at venous end of capillary; some tissue fluid re-enters blood; some tissue fluid drained into lymphatic system
oncotic pressure: pressure caused by osmotic effects of the solutes; tends to pull water back into vessels
Sammer Sheikh