Chapter 28 - Human Nutrition Flashcards
Name the two types of nutrition
Autotrophic
Heterotrophic
What is digestion
The break down of food into particles that are small enough to pass into body cells
What are the two types of digestion
Chemical - enzymes
Mechanical - physical
What are the five sequence of events
- Ingestion - food is take into the alimentary canal (mouth)
- Digestion - food is broken into smaller, more soluble pieces by chemical and physical digestion (mouth, stomach, small intestine)
- Absorption - food passes into the bloodstream and enters the body (small intestine)
- Egestio. - removal of undigested, unabsorbed material (rectum, anus)
Why does mechanical digestion occur in the mouth
Makes food easier to swallow
Creates a greater surface area for enzymes to act
Why does chemical digestion occur in the mouth
Enzymes = amylase
What are the four type of teeth
Incisors
Canines
Premolars
Molars
What are incisors used for
Cutting, slicing, biting
What are canines used for
Gripping, tearing, stabbing
What are premolars and molars used for
Crushing, grinding, chewing
What is the human dental formula
I = 2/2 C = 1/1 PM = 2/2 M = 3/3
What chemical is found in the mouth
Amylase
What does the chemical/enzyme in the mouth do
Breaks down starch to maltose
What is saliva
Made by 3 pairs of salivary glands
Body makes 1 liter per day
Water, salts, mucous, amylase, lysozyme
What does saliva do
Softens and dissolves food Causes food to form into a ball (bolus) Food is pushed back towards the pharynx Epiglottis closes over the trachea Bolus passes down the oesophagus
What does the oesophagus do
Carries food by peristalsis to the stomach
Assisted by mucous and saliva from the lining of the oesophagus
What is peristalsis
Muscular waves that force food through the alimentary canal
What is the stomach
Muscular bag which stores and digests food
Has a sphincter muscle
Lining heavily folded with gastric glands
What is the sphincter muscle
It allows food into stomach
Circular ring of muscle
What is gastric juice
Made up of mucous which coats the stomach
Pepsinogen which is an inactive enzyme that is converted to pepsin by acid, pepsin breaks proteins into peptides
Hydrochloric Acid which has a ph of 1-2, kills bacteria, activates pepsinogen
What is chyme
Thick soupy mixture
Made by churning of stomach
Leaves when pyloric sphincter opens
What is the small intestine made up of
Duodenum
Ileum
What happens in the duodenum
Digestion occurs - enzymes are produced
Inner lining has infoldings called villi which increases surface area
What happens in the ileum
Food entering is fully digested
Nutrients are absorbed into capillaries in the ileum
What are villi
Infoldings in the small intestine They have walls that are one cell thick Rich blood supply In the duodenum - villi produce enzymes In the ileum - villi absorbs water and nutrients
What do capillaries in the villi do
Carries nutrients to hepatic portal vein
They goes to liver
Stores or release nutrients
Deamination
What is lacteal
Lymph fluid
Absorbed fatty acids and glycerol
What is the adaptation of the small intestine
Very long Numerous villi and microvilli Villi walls are very thin Rich blood supply Villi has lymph supply to carry away fats
What is the pancreas
Secretes insulin and digestive materials into duodenum from the pancreatic duct
Pancreatic juice - sodium bicarbonate - neutralists chyme
Enzymes - amylase and lipase
What is the liver
Makes bile - partly formed from remains of red blood cells, yellow/green liquid Functions of bile: Stores in the gall bladder Emulsified lipids - increases surface area for enzymes Neutralizes chyme Functions of the liver: Detoxifies the body - alcohol / drugs Deamination - breaks down amino acids
What is the large intestine
About 1.5. meters long
6cm in diameter
Food stays for 10 hrs to a few days
Consists of the caecum and appendix
What is the function of the caecum and appendix in both humans and herbivores
Humans - vestigial organ, functions unknown
Herbivore - bacteria to digest cellulose
What is the colon
Reabsorbs water - constipation / diarrhea
Makes faeces
What is symbiotic bacteria
Bacteria which lives in humans and benefits humans
- Produces some B group vitamins and vitamin K in the colon
- Bacteria in colon helps break down food - cellulose
- Presence prevents pathogenic bacteria and fungi growing
Describe amylase
Role - digests starch Production site - salivary glands Where it acts - mouth Ph - 8 Product - maltose
Describe pepsin
Role - digests proteins Production site - gastric glands Where it acts - stomach Ph - 2 Product - peptides
Describe lipase
Role - digests fats Production site - pancreas Where it acts - duodenum Ph - 8 Product - glycerol and fatty acids
What is dietary fiber
Consists of cellulose - humans can’t digest it
Prevents constipation - undigested material passes through the colon too slowly / too much water reabsorbed
Absorbs and stores water - unabsorbed material expands in large intestine, stimulates the muscle of the large intestine which stimulates persa
