exam 2 Flashcards
Functions of digestive system
Take food in
Break down into nutrient molecules
Remove waste from the body
Processes definitons
- Ingestion: eating
- Propulsion
Moves food through GI tract (swallowing) (voluntary)
Peristalsis (involuntary) - Mechanical digestion
Chewing, churning, segmentation - Chemical digestion
steps in which enzymes secreted into lumen of GI tract break down complex food molecules to their mechanical building blocks
-Absorption
Passage of digested end products from lumen of GI tract through mucosal cells by active/passive transport into blood or lymph - Defecation
Eliminates indigestible substances from the body via anus in the form of feces
Segmentation:
mixes food w digestive juices and makes absorption more efficient by repeatedly moving different parts of food mass over intestinal walls
Which Papillae house the taste buds
Fungiform, Vallate, and Folliate
Two primary sections and fucntions
GI Tract (alimentary canal)
Digest foods, break it into smaller fragments, and absorb digested fragments.
Mouth, pharynx, esophagus, stomach, small intestine, large intestine
Accessory organs
Teeth, tongue, gallbladder, digestive glands, liver pancreas
Produces secretions that help break down foodstuff
Regulation of digestion
provocation: Mechanical and chemical stimulation
Effectors: smooth muscle and glands
Control: neurons and hormones
Prime mean for regulation is to control the luminal conditions
Splanchic circulation
the blood flow to the abdominal gastrointestinal organs including the stomach, liver, spleen, pancreas, small intestine, and large intestine
the hepatic portal circulation collects nutrient rich venous blood draining from digestive viscera & delivers to the liver
Histology of GI tract
- Mucosa- innermost layer
-simple columnar epithilum - Submucosa- Areolar CT
- Muscularis Externa
- Circular layer- (deep layer) smooth muscle & forms sphincter
- Longtitufianl layer- (superficial layer) smooth muscle
- Serosa or retroperioneal
- serosa: Areolar CT w/ mesothelium, simpel squamous epithil.
- Retroperitoneal has both adventitia & serosa
functions of 4 layers of GI Tract
mucosa,submucosa….
Mucosa-
secrete mucus digestive enzymes, & hormones
Absorbs end products of digestion into the blood
Protect against infections disease
Submucosa-
contains supply of blood & lymphatic vessels, lymphoid follicles, nerve fibers that supply surrounding tissues
Muscularis externa
Responsible for segmentation and peristalsis
Serosa
only present in abdominal cavity
Serosa replaced by adventitia
Retroperitoneal have both adventitia and serosa
Nerves
helps control activity of glands
Enteric (intrinsic vs. extrinsic
intrinsic
- short reflexes which respond to stimuli within GI tract
Extrinsic
- long reflexes allow extrinsic controls to influence digestive activity
-Connect GI tract to brain and spinal cord
Myentric
lies between circular and longitudinal muscle of muscularis externa
Mouth histology + lips n cheek histolgy & function
Mouth- stratified sqaumous epithilum
Lips & cheek
- helps keep food between teeth
- Skeltal muscle covered externally by skin
hard & soft palate
- Palate- forming of the roof of mouth
- Hard palate is anterior & underlain by palatine bones
- Soft palate is posterior & formed mostly of skeletal muscle that rises to close off nasopharynx when swallowing
Tongue muscles (intrinsic & extrinsinc)
Intrinsic skeletal muscle: not attached to bone, allow tongue to change shape but not position
Extrinsic skeletal muscles: alter tongues position, allow to move side to side, retract it, and protrude it & extend to tongue from points of origin on bones of skull or soft palate
Papillae
Filiform papillae - most anterior,smallest and most numerous, contains keratin, rough surface helps for licking and manipulating foods
Fungiform papillae- scattered widely, each have vascular core give reddish hue
Vallate papillae- V-shaped row @ back of the tongue
Foliate papillae- located lateral aspect of posterior tongue
Salivary glands (intrinsic & extrinsic)
Intrinsic- Scattered through oral cavity mucosa augment the output slightly
Extrinsic-Lie outside the oral cavity and empty secretions into it
Salivary glands
-Parotid
- submandibular
- Sublingual
locations & functions
- Parotid
- anterior to ear
- Help w/ chewing, digestion, and keeping the mouth lubricated
- Submandibular
- helps w/ digestion, cleaning, swallowing, & taste
- medial aspect of the body of the mandibular body
- Sublingual
- helps w/ dental hygiene and lubricates mouth
-Lies anterior to the submandibular gland under the tongue
Salivary gland cells
- Serous
produce watery secretion containing enzymes, ions, and tiny bit of mucin - Mucous
Produce mucus
Saliva composition
97-99.5% of water
The rest is composed of
Electrolytes
digestive
Enzymes
Protein mucin, lysozyme and IgA
Metabolic waste
Saliva control & amount
- Control
Controlled by parasympathetic division of autonomic NS - Amount
Average output of saliva is about 1500 mL/day
What are two sets of teeth
Primary and permanent dentitions
Primary: consists of deciduous teeth or baby teeth
permanent teeth are js permanent
Teeth names & function
Incisors (central & lateral) - cutting/nipping food off pieces of food
Canine- tear and pierce
Premolars- grinding and crushing
Molars- grinding and crushing
Third molars (wisdom)
Teeth #s
primary & permanent
Primary has 20 teeth
Permanent has 32 teeth
Teeth structure
Two major regions: crown and root
Root: portion of tooth embedded in the jaw bone
Teeth
Crown, Neck,Cavity,Gingiva,Cells
- Crown
Is exposed part of the tooth above gingiva or gum - Neck
Connects the crown and the root - Cavity
result from bacterial action that gradually demineralized enamel and underlying dentin - Gingiva
Surrounds tooth like a tight collar - Cells
Odontoblast: cell type that secretes and maintains the dentin
Pharynx Histology & function in digestive system
- ONLY passageway for food
- straitified squamous epithilium
Esophagus Histology
10 inches long
Mucosa- Stratified squamous to simple columnar & Folds when empty
Submucosa- Areolar CT contains Esophageal glands
Muscularis externa is Skeletal to smooth muscle
Instead of Serosa its fibrous CT
Heartburn
Super acidic pH (1-3)
Gastroesophageal reflux
Gastric juices may enter esophagus when diaphragm does not reinforce sphincter
Digestion procces in mouth
- mastication- chewing
- deglutition: Buccal phase: voluntary, it ends when food bolus or “bit of saliva” leaves the mouth and stimulates tactile receptors in posterior pharynx
- Deglutition: pharyngeal-esophageal phase:Involuntary and is controlled by the swallowing center in the brain stem (medulla, lower pons)
Deglutition has two phases
Digestion process in Pharynx
- Once food hits pharynx respiration is momentarily inhibited and all routes except desired one into the digestive tract are blocked off
- Pass food from mouth to stomach
Stomach Anatomy & histology
Anatomy
Lies in the upper left quadrant of peritoneal cavity, nearly hidden by liver and diaphragm
6-10 inches long
Histology
Mucosa - simple columnar epithelium
Submucosa
Muscularis externa - smooth muscle
Oblique (deepest)
Circular
Longitudinal
Serosa
Stomach Digestive process
Propulsion- exhibits peristalsis
Mechanical breakdown - churring action provided by stomach smooth muscle during peristalsis
Digestion - protein digestion begins & is main type of enzyme breakdown that occurs. HCL produced by stomach glands denatures dietary proteins to prepare of enzymatic digestion
Absorption- Not much is absorbed in stomach but two common lipid soluble substances
Stomach regulation
Cephalic
Brain VAGUS NERVE
Gastric secretion occurs before food enters stomach
sight and thought
Stimulation of taste and smell receptors
Long reflexes
stomach regulation
Gastric
Stomach distension activates stretch receptors
Long(medulla & vagus nerve) and short reflexes
Food chemicals & rising pH activate chemoreceptors
G cells → Gastrin release to blood
-During this phase gastrin plays major role in stimulating parietal cells to secrete HCL
-Once food reaches stomach local neural and hormonal mechanisms initiate gastric phase
stomach regulation
Intestinal
presence of partially digested foods in duodenum or distention of duodenum when stomach beings to empty→ intestinal (enteric) gastrin release to blood
Inhibitory stomach regulation
Cephalic- loss of appetite, depression
Gastric- excessive acidity (pH lower than 2); fear, stress, anxiety or flight/fight inhibits
Intestinal- distention of duodenum; presence of fatty, acidic, or hypertonic chyme trigger both neural and hormonal signals to tell stomach enough
Emptying of stomach
Stomach contractions cause emptying
Stomach usually empties within 4 hrs after a meal
Solids remain until they are well mixed w gastric juices and converted to the liquid state
Hydrogen content
- When parietal cells are stimulated H+ is actively pumped into the stomach lumen by h+ K+ ATPases (proton pump) .
- As acid is pumped into the stomach, base (HCO3) is exported into the blood; called alkaline tide
small intestine
Duodenum
- As chyme enters the duodenum receptors in its wall respond to chemical signals and to stretch
- Initiates enterogastric reflex and hormonal mechanisms that inhibit gastric secretion; prevent further duodenal filling
small intestine
- Bile duct
- Pancreatic Duct
- Hepatopancreatic duct
- Hepatopancreatic sphincter
Bile duct- ducts fuse with cystic duct draining gallbladder to form bile duct
Pancreatic duct- carry pancreatic juice from pancreas, unit in the wall of duodenum
Hepatopancreatic duct- (ampulla) opens into duodenum via major duodenal papilla
Hepatopancreatic sphincter- smooth muscle valve
Jejunum & ileum
Jejunum- (8ft)extends from duodenum to ileum
Ileum- (12ft) joins large intestine at ileocecal valve
They both hang in central lower part of abdominal cavity
small intestine
Absorbtion
Circular folds
- slowing movement and allowing time for full nutrient absorption
- deep permanent folds of mucosa and submucosa, folds force chyme to spiral through the lumen
Villi
- Digested foodstuff are absorbed through enterocytes into both capillary blood and lacteal
- most active absorption, gradually narrow and shorten along the length of small intestine
Microvilli (brush border)
- complete the digestion of carbohydrates and proteins in small intestines
- densely packed cytoplasmic extension of absorptive cells of mucosa
small intestine
Histology
- Mucosa- studded w/ tubular glands called intestinal crypts
- Submucosa- areolar CT w/ duodenal glands
- Muscularis externa- typical and bilayered
- Retroperitoneal
small intestine
Digestive process
Carbohydrates and proteins are partially degraded, fat digestion begins, most water and nutrients are absorbed
Li
Liver
Anatomy & lobes
Lobes- 4 lobes
Left lobe, quadrate lobe(next to gallbladder), caudate(top), right lobe(biggest)
Anatomy- occupies most of right hypochondriac and epigastric regions, extending farther to the right of the body midline than left
Liver
Lobules Function
- Producing bile
- store fat soluble viatmins
- detox drugs
- process nutrient rich blood
- hepatocytes
- portal Traid
- Sinusoids
- Kippfer cells
- Bile canaliculi
Hepatocytes- liver cells,can secrete some bile, process blood-borne nutrients, store fat soluble vitamins, play important roles inn detoxification
Portal Triad- six corners made of bile duct, portal vein, & hepatic portal arterial
Sinusoids- enlarged, heavily fenestrated; blood from both hepatic portal vein and hepatic artery proper percolates from traid regions through sinusoids and empties through central vein
Kippfer cells- (hepatic macrophages) remove debris like bacteria and worn out blood cells from blood flow
Bile canaliculi- tiny canals that secreted bile flows through
NAFLD
nonalcoholic fatty liver disease; most common liver disease, caused by obesity and increased insulin resistance associated w/ abnormal lipid metabolism & liver inflammation, no symptoms associated
hepatitis
Cirrhosis
what causes it & definition
last stage of progressive chronic inflammation of liver
Result from severe chronic inflammation of liver due to excessive use of alcohol, NAFLD, or viral hepatitis
Gallbladder Anatomy
Thin-walled muscular sac may appear green when filled w/ bile, next to inferior surface of liver
Gallbladder Function
Stores bile that is not immediately needed for digestion & concentrates it by absorbing some of its water and ions.
When empty its mucosa is thrown into honeycomb like folds, allow organ to expand as it fills
Muscular walls contract to expel; bile into the cystic duct, from there
Gallstones
causation & effects
Can obstruct the flow of bile from gallbladder
Caused by too much cholesterol or not enough bile salts
High risk: Forty + yrs, Fat, Fertile, Female
Gallbladder regulation
Hormones and neural stimulations regulate both the secretion of bile and pancreatic juice and release into the small intestine.
Gallbladder
What is secretin & cholecystokinin
The hormones are cholecystokinin (CCK) and secretin
Secretin- released by low pH and goes to pancreas to release bicarbonate
CCK- helps release/relax sphincter , CCK is stimulated by proteins and fat chyme
Pancreas
Anatomy
Soft gland that extends across abdomen from its tail (next to spleen) to its head which is encircled by c shape duodenum.
Most pancreas is retroperitoneal and lies deep to the greater curvature of stomach
Pancreas
Enzymes
acini: cluster of secretory acinar cells that produce enzyme rich components of pancreatic juice. Cells are full of rough ER & exhibit staining zymogen granules, granules contain inactive digestive enzymes
Pancreas
Regulation
The pancreas releases digestive enzymes into the ducts. The pancreas also helps regulate appetite, stimulates stomach acids, and tells the stomach when to empty.
Large intestine
Function
Absorb most of remaining water from indigestible food residue, stores residues temporarily, eliminate it from the body as feces
Large intestine
Anatomy
No circular folds,villi, or brush borders
Mucosa is thicker, its abundant crypts are deeper (crypts contain hella goblet cells)
Mucosa is simple cuboidal epithelium
large int
Digestive process
- Propulsion- propels feces towards rectum by mass movements
- Motility- As haustra fills w/ food residue the distension stimulates its muscles to contract.
- These movements mix residue which aids in water absorption
Movements mainly seen in colon are haustral contractions, slow segmentation movements last abt 1 min and occur about every 30 min - Defecation- reflex triggers by rectal distention, eliminates feces from body
chemical digestion
Carbs
starts in Mouth, salivary glands break carbs down into oligosaccharides
chemical digestion
Proteins in stomach & small intetsine
- Stomach
Begins in stomach when pepsinogen is secreted by chief cells is activated as pepsin
Pepsin functions in acidic pH range, cleaves bonds involving amino acids, breaking the proteins down into polypeptides & free amino acids - Small intestine
Pancreatic protease break down proteins & protein fragments into smaller pieces & some amino acids
Protein enzymes: trypsin, chymotrypsin, pepsin
Brush border enzymes break oligo- & dipeptides into amino acids
chemical digestion
Carbs absorbtion
- small intestine, pancreatic amylase breaks down starch & glycogen into oligosaccharides and disaccharides
- brush border enzyme break oligo- and disaccharides into monosaccharides
- monosaccharides are contransported across apical membrane of enterocytes
- monosaccharides exit across basolateral membrane by facilitated diffusion
chem dig
Proteins
- Amino acids are cotransported across apical membrane of enterocytes
- Amino acids exit across the basolateral membrane via facilitated diffusion
