Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Digestion Topic 6.1 Functions *Provides fuel for cellular respiration. *Provides raw materials need for the body to grow and maintain itself. 1. Carbs 2. Amino acids (needed for building what?) --Body can synthesize most --8 must be obtained by the diet *Most meat products *Few plants provide all of these, but combining various plants usually will provide them all Note: A vegetarian diet should be carefully monitored to assure all amino acids are being obtained. Especially since the body is unable to store them for very long. Functions cont. 3. Fatty acids (needed for synthesizing membranes and hormones. 4. Vitamins organic molecules needed in small amts. --niacin: component of NAD+ --riboflavin: component of FAD --Vitamin A: component of pigments of the eye 5. Minerals inorganic molecules (ions) needed in small amounts --Sodium, potassium: needed for nerve function --Calcium: needed for bones, muscle, and nerve function --Iron: found in hemoglobin Processes 1. Mechanical Digestion: food is broken into small pieces 2. Chemical Digestion: enzymes break polymers into monomers by adding water (process?) *Amylases: break down sugars (poly to mono) * Lipases: break down lipids (to glycerol and F.A.) * Proteases: break down proteins (to A.A.) Anatomy *Passage of Food Note that almost all the structures are smooth muscle and therefore propel the food through. *Accessory Organs Aid in digestion, but food doesn’t pass through them. Passage of Food We basically have a 20-something foot hollow tube running through our bodies, leading from our mouth to our anus. Food passes through this. Our waste never actually enters our bodies at all—it just moves through this hollow tube. SO, what happens during this passage? (I know your dying to know!) *Mouth: teeth mechanically break down food --incisors: biting --canines: tearing meat (carnivores) --molars: grinding vegetation (herbivores) *Saliva released by salivary glands. --Contains salivary amylase (poly to mono) --Kills bacteria and moistens food for swallowing. Passage of Food cont. *Food passes through pharynx (epiglottis blocks trachea) *Esophagus: tube leading to stomach *Anterior is skeletal to allow control of swallowing; the rest is smooth muscle. *Peristalsis: involuntary wave of contractions that moves through digestive tract * Stomach: stores food *Accordian-like walls that can expand . *Food stays here 2-6 hours. Passage of Food cont. Movement of Food *Cardiac Sphincter regulates entry of food into stomach --Sphincter is simply a circular muscle. *Smooth muscle of stomach wall mechanically break down food. *Glands in the stomach lining secrete substances. 1. Chief cells: pepsinogen 2. Parietal cells: --HCl (denatures proteins for easier digestion) --Pepsinogen (inactive precursor of pepsin) Pepsin is an enzyme (one of very few that don’t end in ase) 3. Epithelium: mucous protecting stomach lining from acid Passage of Food cont. *Pyloric Sphincter: regulates exit of food to small intestine *Exit of acid from stomach can cause problems 1. Exit via cardiac sphincter esophagusheartburn 2. Exit via pyloric sphincter sm. Intestine ulcer Hormonal Control of stomach *Proteins in food release of gastrin from stomach wall release of pepsin and HCl *Small Intestine: site of most digestion and absorption --About 17 feet long, food stays here 3-6 hours 1. Duodenum: digestion; first 25cm, or so, receives enzymes from accessory organs Passage of Food cont. *2 accessory organs: 1. Pancreas: secretes proteases, lipases, amylase into the small intestine 2. Liver: produces bile; (gallbladder stores/releases bile) Bile: helps dissolve fats in water --One end is hydrophilic other is hydrophobic Hormonal Control of duodenum** *Failure of secretin to neutralize the acid ulcers in small intestine. --Due to stress or bacterial infection *We feel full after a fatty meal due to GIP. **See chart on chapter outline Small Intestine cont. (first section = duodenum) 2. Illeum & Jejunum absorption *Absorption relies on active transport and diffusion *Brush border: epithelial cells lining sm. Intestine --Villi and Microvilli create a high surface area to volume ratio to facilitate lots of absorption. --Associated with capillaries to facilitate absorption *Tight junctions prevent food from slipping between cells. *Anything that continues past these sites of absorption can be considered waste. *Large intestine: reabsorbs water from waste; about 4 feet; food stays here up to two days --Diarrhea not enough water reabsorbed --Constipation too much water reabsorbed --Bacteria feed on undigested food (cellulose) *Produces gas (beans contain lots of cellulose) *Rectum stores feces until they can be eliminated *Anus opening that allows the exit of waste --So far, all the muscles of the digestive system have been smooth; fortunately, a skeletal muscle sphincter before the anus gives us control over when to eliminate waste. Review: Mouth pharynx esophagus stomach duodenum large intestine rectum anus GOT IT? Ileum jejunum