Physiology Exam 5

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What is the primary function of the digestive system?

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What is the primary function of the digestive system?

transferring molecules from external to internal environment

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What are the 4 basic digestive processes?

motility, secretion, digestion, and absorption

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Motility

muscular contractions of the digestive tract

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What are the 2 types of motility?

propulsive and mixing

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Propulsive motility

propel or push contents through the tract

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Mixing motility

mixes food with digestive juices and exposes molecules to absorbing surfaces

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Secretion

digestive juices are moved into the digestive tract by the exocrine glands

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Digestion

biochemical breakdown of foodstuffs into absorbable units (monomers)

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Absorption

movement of absorbable units, water, electrolytes, and vitamins from the digestive tract to the blood

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What are the 2 divisions of the digestive system?

accessory digestive organs and the digestive tract

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Accessory digestive organs

salivary glands, liver and gallbladder, exocrine pancreas

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Digestive tract

oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus

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What are the 4 layers of the digestive tract?

mucosa, submucosa, muscularis, and serosa

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Mucosa

protective surface that is specialized in some areas for secretion and absorption

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Submucosa

connective tissue which allows for distensibility and elasticity

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Submucosal plexus

regulates gut activity

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Muscularis

smooth muscle that produces propulsive and mixing movements

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Serosa

outer connective tissue that secretes fluid to prevent friction with surrounding viscera

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What are the 4 factors that maximize digestion and absorption?

autonomous smooth muscle function, intrinsic nerve plexus, extrinsic nerves, gastrointestinal hormones

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Autonomous smooth muscle function

some intestinal cells are pacemaker cells that continuously fluctuate membrane potentials

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Intrinsic nerve plexus

networks of nerve fibers contained within the digestive tract

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Extrinsic nerves

innervate digestive organs through the parasympathetic and sympathetic divisions

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Gastrointestinal hormones

endocrine glands are located in various portions of the digestive tract

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Smooth muscle cells

affects motility

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Exocrine gland cells

secretion of digestive juices

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Endocrine glands cells

secretion of hormones

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What are the functional parts of the digestive system?

tongue and taste buds which stimulate salivary, gastric, pancreatic, and bile secretion

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Secretion in the mouth

saliva begins carbohydrate digestion which facilitates swallowing

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What is saliva production regulated by?

conditioned salivary reflex and autonomic influence

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Pharynx and esophagus

uses propulsion motility move the bolus from the mouth through the esophagus to the stomach

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What does mucus act as?

lubricant and a protective layer

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What are the 2 stages of swallowing?

oropharyngeal and esophageal stage

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Oropharyngeal stage

bolus moves from mouth through the pharynx to the esophagus through propulsive motility

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Esophageal stage

bolus moves through esophagus to the stomach through propulsive motility

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What are the 3 stomach regions?

fundus, body, and antrum

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Fundus of the stomach

a thin muscle layer above the esophageal opening

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Body of the stomach

thin muscle layer that stores food

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Antrum of the stomach

thick muscle layer involved in mixing food

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What are the 3 main functions of the stomach?

stores ingested food until emptied into small intestine, secretes hydrochloric acid and enzymes, and mixing motility pulverizes food and mixes with secretions

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What do parietal cells secrete?

hydrochloric acid which activates pepsinogen

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What do chief cells secrete?

pepsinogen

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What does pepsinogen do?

converts to pepsin which initiates protein digestion

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G cells

secrete the hormone gastrin in response to proteins in the stomach

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Enterochromaffin-like cells (ECL)

release histamines which acts on parietal cells to speed up HCl secretion

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D cells

release somatostatin which inhibits secretions by parietal cells, G cells, and ECL cells

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Cephalic phase

thinking about smelling, or tasting the food before food arrives

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Gastric phase

protein stimulates secretion of hormone gastrin which promotes secretion of HCl pepsinogen

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Intestinal phase

inhibitory effects from small intestine which slows gastric secretion to regulate emptying

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What are digested in the stomach?

carbs and protein

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What can be absorbed in the stomach?

ethyl alcohol and aspirin can be but not food or water

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What does the food mix with in the duodenum?

small intestine secretions, exocrine secretions, and liver secretions from bile ducts

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What does the biliary system contain?

liver, gallbladder, and associated ducts

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Proteolytic enzymes

digest proteins into small peptide chains and amino acids

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Pancreatic amylase

digests polysaccharides into disaccharides

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Pancreatic lipase

only secretion to digest fat

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Aqueous alkaline secretion

neutralizes chyme and promotes pancreatic enzyme action

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What are the functional parts of the small intestine?

duodenum, jejunum and ileum

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Duodenum

does a lot of the digestion and absorption

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Jejunum and ileum

finishes the process and aids in mixing

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Segmentation of duodenum

initiated by distension from chyme

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Segmentation of ileum

result of gastrin secretion from chyme goes into stomach

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Migrating motility complex

when segmentation stops between meals and occurs after most absorption has occurred

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Aqueous salt and mucus solution

provides lubrication and protection and provides H2O for hydrolysis

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Na+ absorption

passive in between epithelial cells and active through epithelial cells

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Vitamin absorption

mostly passive absorption

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Electrolyte absorption

iron and calcium absorption are regulated

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Carb and protein absorption

absorbed via secondary active transport into cells

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Fat absorption

passively absorbed through micelles

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Functional parts of the large intestine

cecum, colon, appendix, and rectum

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Haustral contractions

slow mixing movements which shuffle contents back and forth

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Mass movements

happens 3-4 times a day usually after meals where parts of the colon contract simultaneously

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Anabolism

synthesis of larger macromolecules from smaller monomers which requires energy input

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Catabolism

breakdown of macromolecules into monomers though hydrolysis and oxidation after anabolism if needed

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Energy input

comes from ingested food and is released when molecule bonds are broken

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Energy output

comes from the use of energy either through internal work or external work

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External work

energy used to produce mechanical work

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Internal work

activities necessary to sustain life

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Essential nutrients only in food

amino acids, fatty acids, vitamin D and vitamin C

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What stimulates hunger?

neuropeptide

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What suppresses appetite?

melanocortins

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Alpha cells

glucagon

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Beta cells

insulin

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What are the functional glands of the endocrine system?

pituitary, thyroid and parathyroid, adrenal, pancreas, gonads, thymus

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Where do non-polar hormones bind to?

can pass through plasma membrane and bind to the receptor within the organ

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