Flashcards in Human Physiology Deck (72)
Explain why digestion of large food molecules is essential. (2)
1. Food needs to be broken down and reassembled as may not be suitable originally.
2. Large food molecules need to be broken down into smaller ones in order for absorption to occur
Explain the need for enzymes in digestion. (3)
1. Enzymes break down large food molecules into smaller ones.
2. As biological catalysts, they speed up the process of digestion by lowering the activation energy for the reaction.
3. Work at body temperature.
Outline the function of the mouth (3)
1. Chewing (mechanical digestion)
2. Saliva from the saliva glands moistens food to make a bolus for swallowing
3. Amylase begins chemical digestion of starch (polysaccharide digestion)
Outline the function of the Oesophagus (1)
1. A wave of muscles contractions (peristalsis) pushes the bolus into the stomach
Outline the function of the stomach (3)
1. Muscular contractions continue mechanical digestion
2. HCL Acids kills bacteria and provides optimum pH for pepsin
3. Pepsin begins digestion of proteins
Outline the function of the small intestine (4)
1. Bile from the liver and gall bladder neutralizes acid and emulsifies fats
2. Pancreatic amylase and lipase digest carbohydrates and fats ( enzymes from pancreas and intestinal walls)
3. Trypsin digests polypeptides to amino
4. Lower half of small intestine absorbs nutrients into the blood, via the villi
Outline the function of the large intestine (2)
1. Water is absorbed and returned to the blood, leaving semi-solid faeces. This is stored in the rectum
2. Egestion - faeces (containing undigested food, dead cells and other waste) is forced out of the anus
What is mechanical digestion? (2)
Food is physically broken down into smaller fragments via:
1. Chewing (teeth->tongue->bolus->oesophagus)
2. Churning (Stomach->chime->duodenum)
3. Segmentation (contraction and relaxation of non-adjacent segments of circular smooth muscle in the intestine)
What is chemical digestion? (3)
Food is chemically broken down by chemical agents such as:
1. Stomach Acids (gastric glands->digestive acids -> mucous membrane->pancreas->alkaline compounds)
2. Bile (liver->gall bladder->intestine->emulsifies lipids)
3. Enzymes (pancreas->amylase->protease->lipase)
Definition of digestion
Breaking down of complex molecules into simpler molecules to transport around the blood stream
What the anatomy of the digestive system consist of? (2)
1. The alimentary canal consists of organs which food passes through (oesophagus, stomach, small/large intestine)
2. The accessory organs aid in digestion but do not actually transfer food (salivary glands, pancreas, liver, gall bladder)
Definition of peristalsis and its importance (3)
Muscular contractions (both around and down the alimentary canal) that moves food through the digestive tract
1. Contraction of smooth muscles behind the bolus forces it forward
2. Waves of muscle contractions move bolus towards the stomach
3. This is important because food travels in one direction only. This ensures that it only moves forward. Also in the intestine it enables the chyme to mix and churn with enzymes.
Describe the structure of the small intestine
The small intestine contains four distinct tissue layers from the lumen
1. Mucosa: Inner lining, includes villi
2. Submucosa: Connective tissue (between the mucosa and muscle)
3. Muscular layer: Inner circular and outer longitudinal muscle perform peristalsis
4. Serosa: Protective outer layer
It also contains the inner epithelial cell and villi
Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion (8)
1. Many villi increase the surface area for absorption.
2. Epithelium is only one cell layer thick and so food is quickly absorbed.
3. Microvilli on the villi increase the surface area for absorption further.
4. Protein channels and pumps are present in the microvilli for rapid absorption.
5. The mitochondria in the epithelium provide ATP needed for active transport.
6. Blood capillaries are very close to the epithelium so diffusion distance is small.
7. The lacteal takes away fats after absorption.
8. Rich blood supply maintain concentration gradients between lumen and the blood
What is the difference between absorption and assimilation? (2)
1. Absorption refers to the uptake of broken down molecules into the blood (e.g function of the small intestine).
2. Assimilation occurs when the food molecules becomes part of the bodies tissue and are used.
Give an example for every transport mechanism in the digestive system (5)
1. Simple diffusion - Fatty acids passing through the plasma membrane into the epithelial cells
2. Facilitated Diffusion - When the concentration of glucose is higher in the lumen than in the epithelial cells
3. Membrane Protein Pumps - When the concentration in the lumen is lower than in the epithelial cells but the cells need more glucose
4. Endocytosis - Larger molecules that haven’t been fully digested
5. Osmosis - The absorption of water and dissolved molecules occurs in both the small and large intestine
Describe the process of starch digestion (4)
1.Begins in the mouth with salivary amylase.
2. Yet this doesn’t completely breakdown the starch because the enzyme is destroyed by the acidic environment of the stomach
3. The pancreases then secretes pancreatic amylase into the small intestine which finishes breaking down the starch into maltose (a disaccharide)
4. Within the small intestine, there is another enzyme (maltase) that finishes breaking down maltose into 2 glucoses
What is the structure and function of arteries? (4)
Arteries carries high pressure blood away from the heart and to the rest of the body
1. Thick outer layer of longitudinal collagen and elastic fibres to prevent leaks and bulges and keep blooding flowing. Also allows expansion and contraction
2. Thick wall of collagen to withstands high pressure and prevent rupture
3. Thick layers of circular elastic fibres and muscle fibres to pump blood.
4. Narrow lumen to maintain high pressure.
What is the structure and function of veins? (3)
Veins carries low pressure blood back to the heart using valves to ensure blood flows in the correct direction
1. A very wide lumen (relative to wall thickness) to maximize blood flow for more effective return
2. A thin wall containing less muscle and elastic fibres as blood is at low pressure
3. Valves to ensure blood only flows one way to prevent back-flow of the blood and therefore ensures that blood moves towards the heart
What is the structure and function of capillaries? (3)
Capillaries exchange materials between cells in tissues and blood while travelling at low pressure
1. Blood slowly moves through them under low pressure providing opportunities for exchange of substances
2. Very small diameter (~5 μm) which allows the passage of only a single red blood cell at a time (optimal exchange)
3. Outer wall is only 1 cell thick which allows for easy diffusion of substances in and out of the capillary. Due to this distance many capillaries contain pores to aid in the transport of materials between tissue fluid and blood
Outline the structure of the heart (3)
Two atria (receives blood)
Two ventricles (pumps blood)
2. Heart valves
3. Blood Vessels
Pulmonary artery:Sends blood to heart, low O2 concentration,
Pulmonary vein: Sends blood away from heart, high O2 concentration
What are the structural and function differences between
the atria and the ventricles?
1. The atrium is a chamber in where blood enters the heart, the ventricle is a chamber where blood is pushed out of the heart
2. The walls of the ventricle are thicker than the atria because:
o They have to pump blood all the way from the heart to the whole body
o A strong muscle contraction is needed to produce enough pressure to carry the blood the whole way
o The right ventricle only has to pump to the lungs, which is closer, and the left ventricle has to pump all the way to the rest of the body
Outline the stages occurring within the heart? (6)
1. Atria collect blood from veins.
2. Atria contract, atrioventricular valves open.
3. Blood is pumped into ventricles.
4. Ventricle contracts, atrioventricular valves close and semilunar valves open.
5. Blood is pumped into arteries, semilunar valves close.
6. Cycle repeats.
What is the definition of diastole?
When a chamber is relaxed, it causes a decrease in pressure and allows blood to fill the chamber
What is the definition of systole?
When a chamber contracts, it causes an increase in pressure and forces blood out of the chamber through any available opening
What is a cardiac cycle? (2)
1. A cardiac cycle is a series of events from the beginning of one heart beat to the beginning of the next, commonly referred to as one heartbeat. This includes atrial and ventricular contractions (average of 72 cardiac cycles per minute, 1 every 0.8 seconds)
2. It is comprised of a period of contraction (systole) and relaxation (diastole)
Outline the control of the heartbeat (5)
1. Heart muscle can contract by itself (myogenic muscle contraction = spontaneous, independent of nervous system)
2. Pacemaker initiates contractions.
3. The medulla oblongata senses the increase CO2 levels due to respiration
3. One nerve carries messages from the medulla to SA node/pacemaker to speed up the beating of the heart.
4. One nerve carries messages from the brain to the pacemaker to slow down the beating of the heart.
5. Adrenaline signals the pacemaker to increase the beating of the heart.
What was the significance of William Harvey's discovery? (2)
1. People use to think that blood was produced by the heart and was slowly used up by tissues in the body (Therefore doctors would use leeches to suck out the diseased blood)
2. William discovered that the blood is circulated and recirculated through the body (not used up) and that the heart is a double pump.
What is blood composed of?
Blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets while nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat are all transported by the blood.