Module 4 - The Digestive System

teeth: crown

visible portion

teeth: root

invisible portion, embedded in the dental alveolus

teeth: neck

between crown and root, near gum line

teeth: pulp cavity

hollow center within crown that is enclosed by dentin and filled with dental pulp

teeth: root canal

narrow extensions of pulp cavity that contain nerves and blood vessels, runs through root of tooth, has opening at base called apical foramen that vessels and nerves enter through, blood vessels nourish, lymphatic vessels offer protection, nerves provide sensation

how many teeth as child? what are they called?

20; deciduous

how many adult teeth? what are they called? what about molars?

32; permanent; not everyone gets all their molars

in conjunction with the __ , the teeth push food into a bolus via __

tongue; mastication

teeth: pulp

soft gel in pulp cavity, connective tissue containing blood/lymphatic vessels and nerves

teeth: dentin

hard matter that cover pulp, makes majority of internal tooth, gives tooth basic shape and rigidity, dentin hypersensitivity

teeth: enamel

covers dentin in crown, mainly calcium phosphate and calcium carbonate, hardest substance in body, protects tooth from wear/tear of chewing, protects against acids that can easily dissolve dentin,

teeth: cementum

covers dentin in root, attaches root to periodontal ligament

teeth: periodontal ligament

attaches root to alveolar process, acts as shock absorber during chewing

teeth: gingiva

gums, covers alveolar processes

teeth: incisors

single root, blade shaped, 4 front in top/bottom, biting teeth

teeth: cuspids/canines

single root, cone shaped, for tearing, posterior to incisors,

teeth: bicuspids/premolars

1 or 2 roots, flat crowns w ridges, for grinding

teeth: molars

3 or more roots, flat crowns w ridges, for grinding and crushing

tongue

move food for chewing, shape food into bolus, force food to back of mouth for swallowing, speech, taste, secretes mucus/lingual lipase

pairs of salivary glands

parotid, sublingual, submandibular

what do salivary glands do?

secrete saliva that softens/moistens/dissolves foods, cleanses mouth and teeth, initiates digestion of starch

what starts digesting starches?

salivary amylase

where are parotid salivary glands?

inferior and anterior to ears in cheeks

where are sublingual salivary glands?

under tongue

where are submandibular salivary glands?

under floor of mouth

parotid glands secrete what enzyme?

salivary amylase that stars digesting starches

what does saliva do?

lubricates and dissolves foods and begins chemical breakdown of carbohydrates and lipids

what is saliva made up of?

mostly water and solutes and enzymes like sodium, potassium, chloride, bicarbonate, and phosphate, lysozyme, salivary amylase

the order of the ducts, starting from right hepatic duct and ending at pancreatic duct

right and left hepatic ducts join to create the common hepatic duct which joins the cystic duct from gallbladder to form bile duct and the pancreatic duct joins it and enters duodenum

function of ingestion

taking food into mouth

function of processing

physically breaking down food substances into smaller particles to undergo chemical digestion more efficiently

function of digestion

mechanical and chemical breakdown of food

function of secretion

release of water, acid, buffers, enzymes into lumen of digestive canal

function of absorption

passage of digested products from digestive canal into blood plasma and lymph plasma

function of elimination

elimination of feces from digestive canal

function of visceral peritoneum

aka serosa, covers some organs in peritoneal cavity and is their serosa, portion of serosa covering stomach and at lesser curvature of stomach the visceral peritoneum extends up to liver as lesser momentum and at greater curvature of stomach continues down as greater omentum and drapes over intestines, gallbladder, small intestine, produces peritoneal fluid

function of parietal peritoneum

lines wall of abdominal cavity, produces peritoneal fluid

function of mesentery

fan shaped fold of peritoneum that binds jejunum and ileum of small intestine to posterior abdominal wall, suspend abdominal organs

function of lesser omentum

superior, stabilizes stomach, connects stomach and duodenum to liver

function of greater omentum

4 layers, inferior, attachments along stomach/duodenum and extends down anterior to small intestine and turns and extends up and attaches to transverse colon, supports intestines

function of mesocolon

2 separate folds of peritoneum that bind transverse colon and sigmoid colon of large intestine to posterior abdominal wall, with help of mesentery=lock organs into place

function of falciform ligament

stabilizes liver and attaches it to anterior abdominal wall and diaphragm, liver is only digestive organ attached to anterior abdominal wall

site of production/action, function, substrates, productions of SALIVARY AMYLASE

produced by salivary glands, acts in mouth, enzyme that starts breakdown of starches in mouth into smaller molecules like maltose/maltotriose/dextrins

site of production/action, function, substrates, productions of PANCREATIC AMYLASE

produced by pancreatic acing cells, acts in small intestine, enzyme that digests starch (substrate) in small intestine (duodenum) and breaks them down into maltose/maltotriose/dextrins

site of production/action, function, substrates, productions of PEPSIN

secreted by chief cells in stomach, acts in stomach, digests proteins, breaks peptide bonds between AAs and breaks protein chain of many AAs into smaller peptide fragments, substrates are proteins, products are peptides

site of production/action, function, substrates, productions of TRYPSIN

produced by pancreatic acinar cells, acts in small intestine (duodenum), acts on proteins (substrates) and produced peptides (products)

site of production/action, function, substrates, productions of PANCREATIC LIPASE

secreted by pancreas into small intestine (site of action), digests oils and fats (triglycerides as substrates), fatty acids/monoglycerides (products) from pancreatic acinar cells

explain hydrolysis reactions

during digestion, decomposition reactions break down large nutrient molecules into smaller molecules by addition of water molecules; enable dietary nutrients to be absorbed into body

list site of production, stimulus, target organs, and function of GASTRIN

produced by G cells of gastric glands, stimuli: distension of stomach by chyme/partially digested proteins in chyme/high ph of chyme due to presence of food in stomach/caffeine in gastric chyme/ach released from parasympathetic neurons (stimuli), stimulates gastric glands (target organ), stimulates gastric glands to secrete large amounts of gastric juice and increase gastric motility and promotes growth of gastric mucosa (function)

list site of production, stimulus, target organs, and function of GIP

secreted by small intestine (enteroendocrine cells) in response to presence of food (stimulus), stimulate release of insulin from pancreas to control blood glucose levels, targets pancreas, inhibits gastric secretion of absence of proteins

list site of production, stimulus, target organs, and function of SECRETIN

secreted by enteroendocrine cells in small intestine, stimulated by acidic chyme, causes buffering of acid in chyme that reaches duodenum and slows production of acid in stomach and inhibits secretion of gastric juice and promotes normal growth and maintenance of pancreas

list site of production, stimulus, target organs, and function of CHOLECYSTOKININ (CCK)

secreted by enteroendocrine cells in small intestine, stimulated by protein and fat, targets pancreas and gallbladder, stimulates secretion of pancreatic juice rich in digestive enzymes/causes ejection of bile from gallbladder/causes feeling full/inhibits gastric emptying/promotes normal growth and maintenance of pancreas/enhances effects of secretin

role of vagus nerve in digestion

from neck down to second segment of transverse colon, supplies motor parasympathetic fibers to all organs, stimulate gastric glands to secrete gastric juice, increase digestive canal secretion and motility by increasing activity of ENS neurons

role of submucosal plexus in digestion

in submucosa, derived from myenteric plexus, motor parasympathetic/sensory neurons, motor neurons supply secretory cells of mucosal epithelium which controls secretions of organs in digestive canal, regulates digestive canal secretion

role of myenteric plexus in digestion

between longitudinal and circular muscle layers, in esophagus/stomach/intestine, motor sympathetic/parasympathetic, controls digestive canal motility (movement) especially frequency and strength of contraction of muscular layer, regulates digestive canal motility

characteristics of cephalic phase of digestive activity

begins when see/smell/taste/think of food, uses PNS, lasts only minutes, stuff activates cerebral cortex/hypothalamus/brain stem then activates cranial nerves, purpose of phase is to prepare mouth and stomach for food that is about to be eaten

characteristics of gastric phase of digestive activity

begins with food entering stomach (distension/ph changes/undigested proteins), lasts 3-4 hrs, neural and hormone mechanisms regulate gastric phase to promote gastric secretion and gastric motility, hormone gastrin involved in this phase

characteristics of intestinal phase of digestive activity

begins when chyme and food enters small intestine, controls rate of gastric emptying, reflexes here have inhibitory effects that slow exit of chyme from stomach which prevents duodenum from being overloaded with more chyme that can handle, promote continued digestion of foods that have reached small intestine, activities of this phase regulate by neural and hormonal mechanisms, enterogastric reflex occurs, gastric motility inhibited and increase in contraction of pyloric sphincter which decreases gastric emptying, cholecystokinin and secretin

peristalsis

happens during esophageal stage, contractions of circular and longitudinal layers of muscular layer that push food bolus forward, circular muscles contract BEHIND bolus and relax AHEAD of bolus, longitudinal muscles contract AHEAD of bolus

segmentation

churning motions that break bolus with the help of chyme, mixes chyme with digestive juices and brings food into contact with mucosa for absorption

deglutition

aka swallowing, mechanism that moves food from mouth into stomach, 3 stages: buccal, pharyngeal, esophageal

buccal phase of deglutition (swallowing)

first phase, voluntary, bolus passed into oropharynx

pharyngeal phase of deglutition (swallowing)

second phase, involuntary, swallowing reflex controlled by medulla and pons, bolus moves through oropharynx and laryngopharynx and then into esophagus

esophageal phase of deglutition (swallowing)

third phase, involuntary, starts when bolus enters esophagus, peristalsis pushes bolus onward

mastication

aka chewing, food manipulated by tongue and ground by teeth and mixed with saliva, result is food that is soft/flexible/easily swallowed bolus, salivary amylase then begins digestion of starches and lingual lipase acts on triglycerides

bolus

food that was reduced to soft/flexible/easily swallowed mass by mastication

chyme

semifluid mixture of partly digested food and digestive secretions found in stomach and small intestine during digestion of a meal

catabolism

breakdown of organic molecules that released energy, exergonic: release more energy than consume

anabolism

build up of organic molecules, endergonic: consume more energy than produce, performs structural maintenance/repairs, supports growth, produces secretions, build nutrient reserves

metabolism

chemical reactions of the body and are 2 types: catabolism and anabolism

site of production and effects of INSULIN

released by pancreatic beta cells, inhibits lipolysis: lack accelerates pace of lipolysis, stimulate protein synthesis, stimulates active transport of AAs into body cells, increase activity of enzymes needed for anabolism and synthesis of storage molecules, decrease activity of enzymes needed for catabolic reactions, stimulates conversion of glucose to glycogen (glycogenesis) in liver/muscle cells, enhances synthesis of triglycerides in liver/adipose

site of production and effects of GLUCAGON

secreted from pancreatic alpha cells of pancreas, in response to low blood sugar, targets liver, causes increased release of glucose into bloodstream due to gluconeogenesis and glycogenolysis, stimulates glycogen breakdown

where does glycogenolysis happen and what hormones stimulate it? when?

Hepatocytes and skeletal muscle fibers; glucagon and epinephrine; between meals

lipolysis location and what stimulates it?

adipocytes; Epinephrine, norepinephrine, cortisol, insulinlike growth factors, thyroid hormones

what stimulates protein breakdown?

cortisol

gluconeogenesis, where and what stimulates it?

synthesis of glucose from noncarbohydrates; Hepatocytes and kidney cortex cells; glucagon and cortisol

site of production and effects of THYROXINE

from thyroid, thyroid hormones rise=bmr rises, increase bmr by stimulating cellular respiration (calorigenic effect)

site of production and effects of GROWTH HORMONE

from pituitary gland, increase appetite and decrease energy expenditure, increase metabolic rate

site of production and effects of EPINEPHRINE

from suprarenal medullae, enhance triglyceride breakdown into fatty acids and glycerol, stimulate glycogen breakdown, increase metabolic rate, increase appetite and decrease energy expenditure, increase metabolism which increases heat production, stimulates glycogenolysis

primary hormone in absorptive state

insulin

primary hormone during fasting/postabsorptive

glucagon

what is used during fasting/starvation?

fatty acids and ketone bodies for ATP production.

absorptive state

ingested nutrients are entering the bloodstream and glucose is readily available for ATP production

fasting/postabsorptive state

absorption of nutrients from the digestive canal is complete and energy needs must be met by fuels already in the body

absorption of 1 meal takes how many hours? how many hours a day does it consume?

4; 12

postabsorptive state takes up how much of a day?

12

what happens to the fasting/postabsorptive state if you skip meals?

extended

what happens during the absorptive state?

some of the absorbed nutrients are catabolized for the body’s energy needs or are used to synthesize proteins

walls of digestive system from inner to outer

mucosa, submucosa, muscularis, serosa

describe the mucosa

epithelial with glands and goblet cells

describe submucosa

loose connective tissue with blood vessels and lymph nodes

describe muscularis

2 muscle layers, inner is circular and outer is longitudinal

describe serosa

epithelial and secretes fluid to prevent friction

what is the peritoneum lined with?

serous membranes

what is bounded externally by lips (labia) and cheeks?

the mouth

what is lip color due to..

poor keratinization

function of the mouth

analyses and mechanically processes food, lubricates with secretions, begin digestion of carbohydrates

vestibule of mouth

space between lips/cheeks and teeth

fauces of mouth

where food enters oropharynx