Chapter 9: Nutrition and the Human Digestive System Flashcards
The human digestive system comprises of the ________ _____ which starts at the mouth and ends at the anus.
- alimentary canal
What are the six main processes of human nutrition?
- Ingestion
- Peristalsis
- Digestion
- Absorption
- Assimilation
- Excretion/ Egestion
( I Pulled Down Alanβs Ass Eagerly )
What occurs in all the six main nutrition processes?
Ingestion
- food is broken down into soluble molecules
Peristalsis
- food is moved along the alimentary canal by muscular contractions
Digestion
- broken down into soluble molecules
Absorption
- absorbed food molecules taken up by cells for metabolism
Egestion
- undigested and unabsorbed materials removed
What are the 2 types of digestion?
- Physical digestion
- Chemical digestion
Give some general info about physical and chemical digestion.
Physical - chewing in the mouth cavity - peristalsis along the alimentary canal Chemical - reactions are catalyzed by digestive enzymes
Explain physical digestion in detail.
- chewing in the mouth cavity increases the surface area of food particles for enzyme reaction
- allows a bolus to be formed
- peristalsis is produced by alternate contraction and relaxation of the muscles
Explain the chemical digestion in the mouth in detail.
- salivary amylase hydrolyses starch to form maltose
Starch + water β-salivary amylaseβ> Maltose - mouth which has a neutral pH becomes acidic overnight which is where we should use toothpaste
Explain the digestion of protein in the stomach. ( gastric juices and secretion )
- stomach has gastric glands to produce gastric juices
- differentiated cells in the epithelial lining of the stomach wall form different gastric glands
- chief cells secrete pepsinogen which provides an acidic medium for pepsin to function
- parietal cells secrete HCl
- goblet cells secrete mucus
- optimum pH is 2
Explain the digestion of protein in the stomach. ( action of enzymes and function of mucus )
- mucus protects the walls of the stomach from being corroded by acid
- pepsin hydrolysis protein into polypeptides
- rennin converts caseinogen ( soluble ) in milk to casein ( insoluble )
- churned food remains in the stomach for 4h to become chyme
- the chyme is slowly released into the duodenum
What is the function of HCl?
- activate pepsinogen into pepsin
- provides an acidic medium for chemical reactions to occur
- kills bacteria
- stops the action of salivary amylase
The small intestine consists of 2 main parts: ______ and ______. The optimum pH for digestion in the small intestine is ____ ___.
- duodenum
- ileum
- pH 8.5
Chyme from the stomach enters into the ______ and the digestion of _____ starts. Duodenum does not produce any digestive juices but it receives 2 secretions:
- _____ from the liver
- _____ _____ secreted by pancreas
- duodenum
- lipid
- bile
- pancreatic juices
What are the functions of the liver and bile?
Liver
- produces bile ( stored in the gall bladder and released through the bile duct )
Bile
- emulsifies fats
- breaks up large globules into droplets to increase surface area for lipase to act
- prepares an alkaline medium
- neutralizes acid in the chyme
What are the functions of the pancreas and pancreatic juices?
Pancreas
- secretes pancreatic juices: lipase, pancreatic amylase, and trypsin
Pancreatic juices
- lipase hydrolyses fats into fatty acid and glycerol
- pancreatic amylase hydrolyses starch into maltose
- trypsin hydrolyses polypeptide into peptides
The digestion of food is completed in the _____ to produce the _____ _______. The wall of the ileum has intestinal glands which secrete ____ ____ that contains enzymes such as ____, _____, _____, _____ and _____.
- ileum
- final products
- intestinal juices
- maltase
- sucrase
- lactase
- erepsin
- lipase
State the digestion of carbohydrates, proteins, and lipids in the ileum.
Carbohydrates
- maltase hydrolyses maltose into glucose
- sucrase hydrolyses sucrose into fructose and glucose
- lactase hydrolyses lactose into galactose and glucose
Proteins
- erepsin hydrolyses peptides into amino acids
Lipids
- lipase hydrolyses fats into glycerol and fatty acids
The final products of digestion, minerals, vitamins as well as most water are _______ by finger-like projections in the wall of the ileum called ____. The ileum is ____ and ____ to provide a large surface area for absorption of digested food. It has numerous ___ to absorb nutrients.
- absorbed
- villi
- long
- folded
- villi
Explain the structure and the adaptations of villus for the absorption of digested products.
Structure
- tiny projections
- each villus consists of lacteal, blood capillary, and thin epithelium
- epithelium has many tiny projections called microvilli to provide a large surface area
Adaptations
- very thin epithelium = allow rapid diffusion
- a network of blood capillaries = allow rapid absorption
- many lacteals = absorb lipid-soluble vitamins, fatty acid, and glycerol
- many microvilli
Explain the absorption of nutrients in the villus.
Into lacteal:
- fatty acids and glycerols in the form of fat droplets by simple diffusion
- Vitamin A, D, E, and K by simple diffusion
Into blood capillaries:
- Fructose by facilitated diffusion
- Glucose, galactose, amino acids, and minerals by active transport
- Vitamins B and C are absorbed with water which undergoes osmosis
What is assimilation?
- movement of digested food molecules into the cells of the body where they are used
Both the _______ system and ______ system are involved in transporting nutrients that are absorbed into the villi out of the ileum.
- circulatory
- lymphatic
Nutrients are absorbed into the blood capillaries of the villus. These nutrients are transported out of the ileum by _____ _____ ____ to the ____. These nutrients are then distributed to other body cells through the ______ system for assimilation.
- hepatic portal vein
- liver
- circulatory
Nutrients are absorbed into the lacteal of the villus. These nutrients are transported out of the ileum by a ______ vessel called _____ duct for _____ in the lymphatic system before they are finally returned to the circulatory system via the left _______ ___.
- lymphatic
- thoracic
- circulation
- subclavian vein
Explain the assimilation of glucose.
- glucose is used in cellular respiration
- excess glucose is converted into glycogen and is stored in the liver and muscle cells
- if blood glucose level is low, glycogen is converted to glucose
- glucose can also be converted to fat when there is excess glycogen
Explain the assimilation of amino acids and lipids.
Amino acids
- used to synthesis proteins such as fibrinogen and prothrombin
- Excess cannot be stored so converted into urea through deamination
- transported to the kidney to be excreted through the urine
Lipids
-synthesis about 80% of cholesterol
- can be broken down into glucose if required
What is defaecation?
- process where feces is removed from the body which is controlled by the muscles around the rectum of the large intestine and anus
What is the function of the large intestine?
- reabsorption of water in the colon
- synthesis of vitamin K and B12 by bacteria in the caecum
- faeces formation
Explain the formation of faeces.
- undigested food passes through the caecum, colon and rectum by peristalsis
- movement of undigested food is smoothened by mucus
- water is reabsorbed in the colon
- semi-solid material which is called faeces is formed in the rectum
- brown colour of the faeces is due to the bile pigments
- temporarily stored in the rectum before being forced out by muscle contraction which is known as defaecation
What is a balanced diet?
- contains all seven classes of food in the correct proportion according to the needs of the body
Explain the energy value in food.
- quantity of heat produced when 1g of food is completely oxidised
- unit is Jg-1
- 1 calorie = 4.2J
- Formula given is :
Energy value ( kJg-1 ) = Mass of water (g) . Temperature increase/ mass of food sample (g)
Weight loss surgery is one of a variety of procedures opted by obese people to reduce weight. Digestive organs are modified by reducing the size of the stomach by joining the ____ to the ______ which is known as _____ _____ to block absorption of food.
- ileum
- stomach
- gastric bypass
What are the effects of gastric bypass?
- nutritional deficiency
- must voluntarily take minerals and vitamins
- can cause anaemia and osteoporosis
What are the health issues related to defaecation?
- constipation
- colon cancer
- haemorrhoids ( piles )
Explain the health issues related to defaecation.
Constipation
- dry hard faeces which occurs when food moves slowly along large intestine
- abnormally large water is reabsorbed
- causes discomfort
Colon cancer
- caused by prolonged constipation which leads to the accumulation of faeces at the rectum
- toxic substances induce the cells and divide out of control
Haemorrhoids
- due to problems in defaecation
- faeces becomes hard and applies pressure towards the blood vessels in the anus
- blood vessels become swollen or inflamed
What are the health issues related to eating habits?
- gastritis
- muscle dysmorphia
- anorexia nervosa
- bulimia nervosa
Explain the health issues related to eating habits?
Gastritis
- eating late and irregularly
- empty stomach stimulated HCL secretion which acts on the wall and causes inflammation
- sharp pain in the stomach and vomiting
Muscle dysmorphia
- an obsessive mental disorder that carries a delusional belief that their own body is too skinny
- indulge in dietary restrictions and drugs
Anorexia nervosa
- a psychological disorder related to ED
- among young women who feel too fat
- refrains from eating bur exercises excessively
Bulimia nervosa
- a psychological eating disorder
- eat excessively and they induce vomiting or use laxatives
- suffers weight loss and malnutrition
