Human Nutrition (Chapter 29) Flashcards
Nutrition
Nutrition is the process by which an organism obtains and uses its food.
Autotrophic
Autotropic means an organism can make its own food
Heterotrophic
Heterotrophic means that an organism cannot make its own food, but must obtain its food from the environment.
Herbivores
Herbivores are animals that feed exclusively on plants eg. Cattle, sheep, deer.
Carnivores
Carnivores are animals that feed on other animals. They are often called flesh-eaters. eg. fox
Omnivores
Omnivores are animals that feed on animals and plants. eg. humans, bears, badgers.
Digestion
Digestion is the physical and chemical breakdown of food into small soluble pieces which are absorbed into the body.
Long tube starting at the mouth and ending at the anus
Alimentary Canal.
Sequence of events in human nutrition
- Ingestion
- Digestion
- Absorption
- Egestion
Ingestion
This is the taking of food into the alimentary canal. ie. putting food into the mouth.
Digestion
This is the mechanical and chemical breakdown of food.
Absorption
Food absorbed into the blood and enters the body when it passes across the membranes lining the alimentary canal
Egestion
This is the removal of unabsorbed and undigested material from the digestive system.
Incisors
Chisel shaped with sharp edges for cutting, slicing or biting.
Canines
long, pointed teeth. They are poorly developed in humans but well developed in carnivores. They grip, stab and tear food.
Premolars
teeth with projections on the surface called cusps. They crush and chew food.
Molars
the large teeth located at the back of the jaws. They also crush and chew food.
Human Dental Formula
2(I 2/2, C 1/1, PM 2/2 M 3/3)
Chemical Digestion
Takes place due to the action of the enzyme amylase.
Peristalsis
Peristalsis moves food through the alimentary canal. It helps break down food mechanically, mixes food with the secretions of the stomach and forces the mixture into the small intestine.
Stomach
The stomach is a muscular bag that stores and digests food
The lining of the stomach is heavily folded, forming millions of _______
Gastric Glands
Gastric glands produce a range of secretions called
gastric juice
Gastric juice consists of
Mucous (coats the stomach and prevents self digestion)
Pepsinogen
an inactive enzyme- does not digest the cells in the stomach lining that produce it. Converted to the active enzyme pepsin by acid.
Hydrochloric acid (HCI)
Gives the stomach a pH of 1-2. Acid kills bacteria, activates pepsinogen and denatures salivary amylase.
Chyme
The contraction of the stomach walls helps to churn and digest the food mechanically. This turns it into a thick, soupy mixture called Chyme.
Bile
yellow-green viscous liquid. Consists of water, bile salts and bile pigments.
Bile functions
- Emulsifies lipids
- Contains sodium hydrogen carbonate, which helps to neutralise chyme from the stomach (as chyme is acidic)
- Excretes the pigments biliverdin and bilirubin which are made from dead red blood cells.
Small intestine- first 25 cm?
duodenum
5.5 meters in small intestine
ileum.
Function of duodenum
digestion
rectum function
stores faeces
colon function
reabsorbs water from the waste, forming faeces.
vestigial organs
lost former use eg. appendix and caecum
capillaries carry nutrients to, ____
hepatic portal vein
deamination
Amino acids cannot be stored in the body, they become toxic. Deamination is when amino acids not used by the body are broken down in the liver, forming urea.
Adaptations of the small intestine for absorption
- very long
- numerous villi and microvilli
- walls of villi are very thin
- rich blood supply to carry away water-soluble products
- Each villus has a lymph supply to carry away the fats.
