D1a2: Digestion

Process in which food is broke. Down to use as energy

Physical change in food (chewing)

Chemical change in food

Rhythmic muscle contractions in longitudinal muscles (esophagus, stomach, intestines, rectum)

Rhythmic muscle contractions in circular muscles (mixed food)

Mechanical digestion makes food easier to swallow and increases surface area Salivary gland- Begins chemical digestion as saliva contains amylase to break down starch Tongue- determines which foods need to be processed further, shapes food into bolus and then pushed it to the back of pharynx

• Flexible tube that leads to stomach • secretes mucus • passed through diaphram to connect w stomach at lower esophageal spincter (regulates entry and exit)

• Cross crossed muscle layers create churning motions (ingested food and digestive juice=chyme) • Site of food storage and initial protein digestion • Physical and chemical digestion

Strong circular muscles that move good in and out of stomach Lower esophageal spincter contractions closes opening to stomach, relaxation allows food in, prevents regurgitation Pyloric Sphincter- Moves food and stomach acid into small intestines

Gastric glands- makes gastric acid (water ,mucus,HCL,pepsin) • HCL secreted from parietal cell (hormone gastric stimulates release) • conveys pepsinogen to pepsin Pepsinogen (inactive)+HCL=pepsin (active) • hydrolyzes proteins S into smaller polypeptides by breaking peptide bonds

• Chyme leaves stomach and goes here

amino and fatty acids in chyme release CCK (stimulates pancreas to release enzymes and gallbladder to release bile)

• chyme w low ph=hormone secretion (sodium bicarbonate) from pancreas which neutralizes gastric fluid and brings pH to 8

Enterogastron secreted so that time for fat digestion increases as it inhibits secretion of gastric juices and slows peristalsis)

Carbs- hydrolyzed into monosaccharides Proteins- broken down into amino acids Fats- hydrolyzed by lipases into glycerol and fatty acids Dna divested by nuclease=nucleotide

Absorbs nutrients and water from circulatory and lymphatic system Lacteal- absorbs fatty acids and glycerol Capillaries- absorbs nucleotide, monosaccharides and amino acids Epithelial- impermeable barrier between digestive juices and tissues

MR LIM Microvilli- high SA:V ratio Rich capillary network- transports digestive products Lacteals- absorbs lipids from lymphatic system Intestinal glands- exocrine pits release enzymes Membrane protein- facilitated product transport

• Absorbs water • bacteria decompose leftover organic matter • makes vitamin B, K and folic acid (needed to make rbc) • stores and eliminates waste

Where waste leaves

Pancreas- Endocrine cells (hormones): insulin=lower blood sugar and glucagon=raise blood sugar; exocrine cells (gastric juice) Liver- makes bile, secreted surfactants into bile to break lipid droplets Gallbladder- Stores and regulates release of bile

• Secondary active transport- glucose (polar) cannot diffuse simply. Sodium potassium pumps, actively pump sodium ions into the intestine and potassium out creating concentration gradient. Sodium glucose co transporters (proteins) transfer a sodium ion w a glucose into the epithelium (Factiliated) • Simple and Facilitated- Triglycerides must be digested before absorbed. So they are broken down into monoglyceride and fatty acids which are absorbed into villus epithelium cells by simple diffusion. Fatty acids can also be transported by fatty acid transporters (proteins) in microvilli=Facilitated. Once inside epithelium cells monoglyceride and fatty acid combine again and CANNOT diffuse into lumen

Needs proteins to be transported in blood (lipids=water insoluble) • lipid globules are emulsified by bile salts before being chemically digested by pancreatic lipase • components +protein=chylomicrons (go to liver and get converted to solvable lipoproteins

Amylase digests starch Glucose used in cell resp or stored in liver as glycogen)

Serosa- Outer coat Muscle layers- longitudinal muscle and inside it is circular Sub Mucosa- contains blood Mucosa- lining w epithelium