Ch 11: Animal Systems for Life Flashcards
1
Q
What is the circulatory system and what is its four main principal functions?
A
The circulatory system is the transport system of the human body and has four principal functions:
- transportation of water, oxygen and carbon dioxide
- distribution of nutrients and removal of wastes
- maintenance of body temperature
- circulation of hormones.
2
Q
What are the general components of the ciruclatory system?
A
The circulatory system consists of three general components:
- a fluid in which materials are transported, such as blood
- a system of blood vessels or spaces throughout the body in which the fluid moves
- a pump, such as the heart, that pushes the fluid through the blood vessels or spaces.
3
Q
What are the essential features of a transport system?
A
The essential features of a transport system must include the ability to reach every cell in the body, distributing the necessary requirements in a usable form and not disrupting the functioning of other systems in the body.
4
Q
What are the components of the cardiovascular system?
A
Heart, blood and blood vessels make up the cardiovascular system.
5
Q
What are features of plasma?
A
- 55% of blood, pale yellow compnent through which solid blood components, body heat, dissolved gases, nutrients and wastes are transported
- contains a number of dissolved proteins w different functions. These plasma proteins carry other molecules i.e. calcium, drugs, hormones, lipids, vitamins and chlosterol. Also keep the blood pH at optimum (7.35-7.45
6
Q
What are the features of erythrocytes?
A
- Main function is to carry oxygen and carbon dioxide
- Contain haemoglobin which enables the cell to bind oxygen molecules
- Does not have a nucles in mature stage to allow storage of more haemoglobin. Also makes them pliable and elastic so that they can twist and flex as they move through blood vessels that are sometimes narrower than their unbent size
- 5 million red blood cells (or erythrocytes) per cubic millimeter of blood.
- Each cell is shaped like a disc with both flat sides pressed in.
- Measures 8 microm in diameter and about 2 microm thick.
- Red blood cells have a life span of about 4 months.
- Produced in the bone marrow
7
Q
What are the features of platelets?
A
- Function primarily to initiate blood clottingBlood leakage from cut vessel is stopped by platelets.
- Smaller than red blood cells, fragments of cells derived from bone marrow
- Irregularly shaped and move easily through smooth blood vessels when resting
- Clump together to help form a clot
- Life span of one or two weeks
- Release chemicals to contract the blood vessel and reduce blood loss
- Become acitve and rupture if they reach a sharp edge i.e. cut. When this happens, a substance that reacts with proteins in the plasma to create a mesh of fibres is released. This mesh prevents further blood flow. After a few days the fibres contract and begin to close the wound to the blood vessel
8
Q
What are the features of leukocytes?
A
- White blood cells or leukocytes fight infection.
- Larger than red blood cells but fewer in number
- Nucleus helps in classifying them into different groups
- 10,000 white cells/mm3 of blood during infection
- Leukocytes function collectively
- Some white cells live few minutes to days others live for years
- Found in tissue as well as the blood
- Move themselves like an amoeba - they can pass through capillaries by squeezing between the cells that make up the walls and so get to the regions of damaged cells
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9
Q
How does blood transport oxygen?
A
- Red blood cells carry oxygen via oxyhaemoglobin.
- Normally 0.3 mL of oxygen can dissolve in 100 mL of blood. Haemoglobin increases capacity to 20 mL of oxygen per 100 mL.
- When there is high concentration of oxygen i.e. in the capillaries exiting the lungs, oxygen combines with haemoglobin to form oxyhaemoglobin
- Where there is a low concentration of oxygen, as in the tissues, the oxygen molecules dissociate from the haemoglobin. The oxygen diffuses through the red blood plasma membrane, travels through the plasma and out through the cell membranes of the capillary wall to cells with a low concentration of oxygen.
- When the body is at rest, the cells use only about one-quarter of the total oxygen carried in the blood. However, with heavy exercise, more than three quarters of the available oxygen is used. Thus, the body has a large capacity to provide extra oxygen to cells in case of emergencies
10
Q
How does the blood transport carbon dioxide?
A
- Cellular respiration produces carbon dioxide waste so removal keeps cell pH optimal.
- Carbon dioxide is soluble and reacts slowly with water to form carbonic acid, H2CO3(aq). In the RBC, where the initial reaction occurs, the reaction is sped up by carbonic anhydrase.
- CO2 produced by cells:
- 70% carried as carbonic acid in the plasma.
- 23% attaches to haemoglobin in red blood cells.
- 7% as CO2 gas.
- As the blood passes the lungs, the decreasing concentration gradient for CO2 causes all the previous reactions to reverse. The carbonic acid reverts back to CO2 and water. The CO2 leaves the internal environment of the blood, passing the external environment of the lungs where it and water are exhaled as vapour
11
Q
What are the main types of vessels in closed circulatory systems?
A
Arteries
- Arteries take blood away from the heart
- Arteries and arterioles (small arteries) can also narrow when nerves in the vessel walls or chemicals carried in the blood cause the circular muscles in the walls to contract.
Veins
- Veins carry blood to the heart
- The lumen of the vein is larger than that of the artery. More than 60% of the blood is distributed in the veins, which could be seen to act as a reservoir or as extra volume to be pumped around with increased exercise.
- Veins have valves in them to help keep the blood flowing to the heart. This is especially important in the legs. While the legs are moving the blood is squashed in the veins that travel between the muscles. The blood can only move up as the valves prevent it dropping back.
Capillaries
- Capillaries are found between arteries and veins
- Unlike arteries or veins, capillaries have very thin walls and are very narrow. In fact, their walls are only one cell thick. This makes it possible for diffusion of all the nutrients that a cell needs, such as glucose and oxygen, to occur. Wastes, such as carbon dioxide and urea, are also able to pass from the cells to the blood.
- Capillaries are so numerous and so small that every cell in the body is only a few millimetres away from a capillary.
12
Q
What are features of the heart?
A
- function - pumps blood around the body
- is made of muscle and in humans can contract continuously about 70 times/min
- cardiac tissue is found only in the heart
- it is the coordinated contraction of cardiac muscle or myocyte cells that provide the pumping action of the heart
13
Q
What is the pathway of blood through the heart?
A
Deoxygenated blood enters the right atrium, via the vena cava, from the general body system of blood vessels, the systemic circulation, and passes into the right ventricle.
When the right ventricle contracts, blood is forced into the pulmonary artery, which leads to the lungs. This is called pulmonary circulation. Here, oxygen diffuses into the blood and carbon dioxide passes out into the air in the lungs. The now oxygen-rich or oxygenated blood passes back into the heart through the left atrium and then into the left ventricle. When this ventricle contracts, the blood is forced into the aorta, the largest artery, which, through its many branches, takes blood to all parts of the body. The septum keeps the deoxygenated blood on the right side of the heart from mixing with the oxygenated blood on the left side.
14
Q
How is blood kept flowing in one direction?
A
The blood is kept flowing in one direction in the heart by the presence of four valves: one between each atrium and ventricle (the two atrioventricular valves) and one between each ventricle and the artery it leads to (the pulmonary valve and aortic valve). The two ventricles contract at the same time and the atria contract at the same time, but the ventricles and atria contract at different times. This leads to the two atrioventricular valves snapping shut at the same time as the ventricles contract. The pulmonary and aortic valves close when the ventricle finishes contracting, so that blood under pressure from the enlarged elastic arteries does not flow back into the heart.
15
Q
How does the lymphatic system function?
A
- Blood pressure forces some fluid as well as small protein molecules out of the capillaries at the arterial end. Most of the water passes back into the capillaries at the venous end, as the blood pressure has dropped off.
- The water moves back into the capillaries by osmosis, caused mainly by the high concentration of albumin molecules in the plasma.
- Without lymph vessels some water and protein would be left in the spaces between the cells
- Lymphatic capillaries are small, blind-ending tubes. They allow the fluid and protein to enter through tiny flaps that act as one-way valves between the cells in their walls. The fluid flows in the lymph vessels to the heart to rejoin the normal blood circulation. It is pushed along in much the same way as blood in the veins is moved, by contracting muscles. Valves in the lymph vessel walls maintain a unidirectional flow to the heart.
16
Q
What are adaptations of animals for gas exchange?
A
The surface across which the gas exchange occurs needs to:
- be moist, as the gases dissolve in the water and diffuse from one side of the membrane to the other
- be thin and permeable, so the gas molecules can move across it easily and quickly
- have a large surface area in relation to the volume of the organism so as to adequately provide the gaseous requirements
- have a greater concentration of required gas on one side of the membrane than the other so that a concentration gradient is maintained.
19
Q
How is gas exchange’s efficiency optimised in mammals?
A
- The alveoli endothelial tissue provide a moist surface across which gas exchange occurs and increase surface area of the lung tissue enormously.
- There are about 700 million alveoli in the human lung and they provide a surface area that is approximately the size of a tennis court
- The capillaries are so narrow that, as the red blood cells are pushed through them, they are partially squashed into a conical shape.
- This increases the amount of surface area in contact with the capillary wall and ensures there is little fluid between the blood cell and the alveolar wall. This minimises the distance the oxygen and carbon dioxide molecules need to travel (less than 1 mm). Each alveolus is covered, internally, with a thin layer of surfactant fluid, a detergent-like lipoprotein, which reduces its surface tension.
- This prevents the alveolar walls from being pulled inwards so that the alveoli don’t collapse and the lungs can expand.
20
Q
How is our breathing rate controlled?
A
- Air is moved in and out of the lungs by movements of the ribs and the diaphragm.
- Our rate of breathing is controlled mainly by the level of carbon dioxide in the blood.
- Most of the carbon dioxide produced by cells in respiration is converted into carbonic acid in the plasma.
- The bicarbonate ions pass into the blood plasma, where they are transported to the lungs for removal.
- This lowers the carbon dioxide concentration of the blood.
25
Q
What does the digestive system look like?
A
26
Q
What does the stomach look like?
A
30
Q
What occurs during digestion in the small intestine?
A
- digested food moves into the small intestine via peristalsis. This is controlled by the pyloric sphincter (at the base of the stomach)
- small intestine is about 7m long, SA of 4500m2
- pancreatic juice (amylase, trypsin, lipase, bicarbonate-neutralises hydrochloric acid from the stomach that arrives with the chyme and prevents pepsin and protease action as walls of duodenum not protected by mucus) is secreted from the pancreas and enters the duodenum (at the top of the small intestine)
- bile passes down the bile duct from the liver into the duodenum, involved in the mechanical breakdown of fats (detergent like action). Fats are emulsifyed down into smaller pieces, increasing SA for lipase (produced in pancreas), lipase breaks down the fat into fatty acids and glycerol
- trypsin, produced by the pancreas, enters the duodenum and breaks down into smaller-chained polypeptides. Erepsins (pancreas also) completes the digestion of the short-chain polypeptides to individual amino acids
- food then enters the jejunum and the ileum where digestion of all food nutrients continues, digestion of proteins continues until smaller amino acids are available for absorption into the blood and then to the body cells. Carbohydrates keep on being broken down into absorbable form i.e. glucose
31
Q
What occurs during absorption?
A
- Absorption of nutrients can occur along the length of the gut. Substances such as alcohol and some drugs can be absorbed through the stomach wall into the bloodstream. Because of this, the effects of such substances are felt very quickly. However, most nutrients are absorbed along the length of the small intestine.
- In the small intestine, nutrients such as glucose, amino acids, fatty acids and glycerol move from the gut into the blood by means of diffusion and active transport. The structure of the small intestine is perfect for the uptake of nutrients. The lining is moist and thin with a rich supply of blood vessels. Special structures, known as villi, project from the surface of the small intestine tissue, increasing the surface area of the gut lining and thus facilitating efficient absorption. Each villus is supplied with a network of capillaries that intertwine with lymph vessels called lacteals that transport materials.
- Glucose and amino acids are absorbed into the capillary network; fatty acids and glycerol are absorbed by the lacteals and enter the lymphatic system.
- Along with the digested nutrients, water absorption also occurs in the small and large intestines.
38
Q
What are the kidneys?
A
- the main organ of the human excretory system
- two bean-shaped organs, as big as a fist
- kidneys filter water and solutes from blood. Most of this is reabsorbed back into blood, but the excess leaves the kidneys as urine.
- the renal artery, a branch of the aorta, brings blood containing nitrogenous waste and water, blood proteins, RBC and minerals dissolved in the blood plasma to the kidneys. Because the kidneys are the filters that remove wastes from the blood, they may hold as much as 25% of the body’s blood at any given time
39
Q
How does the nephron function and what is its structure?
A
- blood travels from the aorta through the renal artery carrying minerals, water and urea, destined for elimination. At the kidney, blood travels through smaller and smaller blood vessels until it reaches the one of approximately 1 millions functional units called a nephron.
- It is at the nephrons that water and solutes are filtered from the blood and amounts to be reclaimed are adjusted.
- each nephron consists of a ball of capillaries called a glomerulus. The glomerulus is situated inside the Bowman’s capsule. As the capillaries that form the glomerulus are tightly bound into the smaller Bowman’s capsule and pumped by the renal artery, blood in the glomerulus is under very high pressure. This pressure forces out some of the water and all solutes except protein from the blood through tiny pores into the Bowman’s capsule. This filtrate has just moved into the external environment as it has passed through the plasma membrane that separates it from the internal environment.
- The filtrate moves to the proximal tubule, then to a hairpin-shaped loop of Henle and finally to the distal tubule. A collecting duct, the nephron’s last region, is part of a duct system leading to the kidney’s central cavity (renal pelvis), then into a ureter.
- Blood does not give up all of its water and solutes. The unfiltered part flows into capillaries threading around the nephron’s tubular parts. In these capillaries, the blood reclaims water and solutes from the tubules. Then it flows into veins and back to the general circulation.
