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
