Year 1 - Digestion Flashcards
What is mechanical digestion?
Physically breaking down food into smaller particles
Examples of mechanical digestion
Chewing food using teeth in the mouth; muscles contractions of the stomach wall churning food
What is chemical digestion?
Chemically breaking down food using enzymes that perform hydrolysis
What is saliva?
It is a watery secretion, containing mural and salivate amylase and some mineral ions.
What pH is the mouth?
Slightly alkaline - the optimum pH for amylase
What lubricates the oesophagus?
Mucus
What is secreted by the stomach and what is its role?
Mucus and it is there to protect the stomach lining from attack by stomach acid
What is stomach acid made of and what is its role?
It is made of hydrochloric acid and its role is to denature protein to increase surface area, kill pathogens and activate digestive enzymes
What is carbohydrase?
The general term for an enzyme that breaks down carbohydrate.
What are the two polysaccharides of alpha glucose?
Starch (from plants) and glycogen (from animals)
What are starch and glycogen broken down to maltose by?
Salivary amylase in the mouth and the pancreatic amylase
Where is the pancreatic amylase secreted from where is it secreted into?
It is secreted by the pancreas and it is secreted into the small intestine.
What are the three enzymes that the small intestine produces?
Maltase, lactase and sucrose
What does maltase break down and into?
Maltase breaks down maltose to alpha glucose
What does lactase break down and into?
Lactase breaks down lactose to glucose and galactose
What does sucrase break down and into?
Sucrase breaks down sucrose to glucose and fructose
What pH does carbohydrases work the fastest?
At neutral pH
What are the two different types of protease?
Endopeptidase and exopeptidase
What is protease?
They digest proteins
What are endopeptidases?
They hydrolyse peptide bonds within proteins to form short chains of amino acids called peptides
What are exopeptidases?
They hydrolyse peptide bonds at the ends of a proteins to produce either dipeptides or single amino acids
What do exopeptidase produce?
Dipeptides or individual amino acids
What do endopeptidase produce?
Shorter polypeptides
What are the two specific endopeptidase?
Pepsin and trypsin
Where is pepsin secreted?
Gastric glands of the stomach
Where is trypsin secreted?
Pancreas into the small intestine
What is pepsin secreted as?
Inactive pepsinogen
What is trypsin secreted as?
Inactive typsinogen
What is the process of pepsin?
In the stomach, hydrochloric acid changed the structure of pepsinogen to convert into the active pepsin. Pepsin works optimally in the acidic conditions of the stomach.
What is the process of trypsin?
An enzyme called enterokinase activates trypsinogen in the small intestine. Trypsin works optimally under alkaline conditions. Pancreatic juice secreted into the small intestine neutralises stomach acid to allow this.
Why are enzymes secreted in inactive forms?
If they were active in the cell, they would digest the contents of the cell. They need to be inactive within the cell that made them, and then activate outside the cell.
What do dipeptidase do?
Dipeptidase hydrolyse dipeptides to amino acids
What do bile salts do?
Bile salts emulsify lipid globules into smaller droplets. This increases the surface area for lipase to act on.
Where is lipase secreted and into where?
Lipase is secreted from the pancreas into the small intestine
What does lipase do?
It hydrolyses triglycerides to monoglycerides and fatty acids
What is bile?
It is a secretion of the liver. It contains bile salts.
Where is bile stored and where id it released?
Bile is stored in the gallbladder and then released into the small intestine via the bile duct.
What is absorbed into the blood?
Amino acids and monosaccharides
How are amino acids and monosaccharides absorbed into the blood?
By a combination of active transport and facilitated diffusion.
What are absorbed into structures called lacteals?
Fatty acids and glycerols
How are fatty acids and glycerols absorbed into lacteals?
By simple diffusion
Where do lacteals drain into?
The lymph, which later drains into the blood
Why do individual epithelial cells have microvilli?
To increase the surface area for absorption
What does the outer serosa consist of?
A layer of tough connective tissue that protects the wall of the gut and reduces friction from other organs in the abdomen as the gut during the digestive process
What are the two muscles that are in the two layers of muscle on the gut wall?
The inner circular muscle and the outer longitudinal muscle
How does the food move across the muscle layers?
The muscles cause waves of muscular contractions, peristalsis. Then behind the ball of food, the muscles contrast.
What does the sub-mucosa consist of and what are the functions?
It consists of connective tissue containing blood and lymph vessels to take away absorbed food products as well as nerves the co-ordinate the muscular contractions involved in the process of peristalsis
What is the mucosa?
It is the innermost layer and the wall of the gut.
What does the mucosa secrete and what is the purpose?
It secreted mucus which lubricates and protects the mucosa
What does the mucosa secrete in some regions of the gut?
It secreted digestive juices in others it absorbs digested. food.
Why does the mucosa of the small intestine have villi?
To increase the surface area for absorption of nutrients.
What causes scurvy?
Lack of vitamin C
Symptoms of scurvy
Fatigue, feeling miserable, pain in limbs, small red-blue sports on the skin, swollen gums, tooth loss, shortness of breath, easily bruised skin
Explanation of scurvy
Vitamin C is needed to make collagen, a major component of connective tissue is important in cartilage, bones, tendons, ligaments, and skin
What is rich in Vitamin C?
Citrus fruit
What causes rickets?
Lack of Vitamin D
Symptoms of rickets
Skeletal deformities, dental problems, poor growth and development, fragile bones, bone pain, brittle bones, weak bones
Explanation of rickets
Vitamin D increases intestinal absorption of calcium ions. Calcium is needed for strong healthy bones and teeth.
What can you get Vitamin D from?
UV light from the sun helps our skin produce Vitamin D
What causes anaemia?
Lack of iron
Symptoms of anaemia
Fatigue, weakness, pale or yellowish skin, irregular heartbeat, shortness of breath, dizziness or light-headedness, chest pain, cold hands and feet
Explanation of anaemia
Iron is needed to make the oxygen-binding haem groups in haemoglobin. Haemoglobin is needed to transport oxygen in erythrocytes of the blood.
What is rich in iron?
Red meat
What is obesity?
When someone is severely overweight.
What causes obesity?
Excessive calorie intake and lack of exercise can cause obesity
What can be caused by obesity?
arthritis, type 2 diabetes and coronary heart disease
What is an endoscope?
It is a long, thin, flexible tube that has a light source and a video camera at one end. Images from the examination are usually relayed to a television screen. They can be inserted into a natural opening - mouth, or anus. They can be inserted through a small cut in the skin
What is a colonoscope?
Used to examine the colon
What is a gastroscope?
Used to examine oesophagus and stomach
What is endoscopic retrograde cholangiopancreatography (ERCP)
Used to check gallstones.
What are gallstones?
They are small sones, usually made up of cholesterol, that form in the gallbladder. They don’t have any symptoms but if the stone blocks one of the bile ducts, it can cause sudden and severe abdominal pain.
