Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
133 Cards in this Set
- Front
- Back
Primary digestive organs
|
1. mouth
2. oral cavity, teeth, tongue 3. pharynx 4. esophagus 5. stomach 6. small intestine 7. anus |
|
Accessory digestive organs
|
1. salivary glands
2. liver 3. gallbladder 4. pancreas |
|
Primary function of hollow organs
|
breaking down and absorption of nutrients
|
|
Function of the digestive SYSTEM
|
- breaking down and absorption of nutrients
- accessory organs produce secretions containing water, enzymes, buffers and other components that assist in preparing nutrients for absorption |
|
Functions of the digestive TRACT (6)
|
- Ingestion: occurs in oral cavity, foods and liquids enter the digestive tract
-Mechanical processing: occurs in oral cavity and stomach - Digestion: occurs through out GI tract, chemical and enzymatic breakdown of food into small organic molecules that can be absorbed by the digestive epithelium - Secretion: occurs throughout GI tract, although it occurs throughout most acids, enzymes and buffers required for digestion provided by the accessory digestive organs - Absorption: occurs primarily in the small intestine some absorption occurs in the large intestine. Movement of organic molecules, electrolytes, vitamins and water across the digestive epithelium and into the interstitial fluid - Compaction: occurs in large intestine, progressive dehydration of indigestible materials and organic wastes prior to elimination from the body |
|
Function of oral cavity, teeth, tongue
|
mechanical processing, moistening, mixing with salivary secretions
|
|
Function of pharynx
|
muscular propulsion of materials into the esophagus, common passageway for food and air
|
|
Function of the esophagus
|
transport of materials to the stomach
|
|
Function of the stomach
|
chemical breakdown of materials via acid and enzymes; mechanical processing through muscular contractions
|
|
Function of the small and large intestine
|
enzymatic digestion and absorption of water, organic substrates, vitamins and ions
|
|
4 layers of the gastro intestinal tract
|
-Mucosa
-Submucosa -Muscularis Externa -Serosa |
|
What is: Mucosa
|
inner lining of digestive tract is a mucus membrane consisting of cuboidal and columnar epithelium
|
|
What is: Submucosa
|
layer of dense irregular connective tissue. Contains blood vessels, nerves and glands
|
|
What is: Muscularis Externa
|
smooth muscle in 2 layers for movement along tract and mechanical processing (circular muscle=twisting, longitudinal muscle=shortening)
|
|
What is: Serosa
|
visceral peritoneum in most segments. Replaced by adventitia on oral cavity, pharynx, esophagus and anus
|
|
Mesentary
|
- Double sheet of peritoneal membrane with areolar tissue between
- Provides access route for blood vessels, nerves, and lymphatic vessels - Stabilizes position of attached digestive organs |
|
Mucosa Components - Epithelium
|
- Tract begins and ends with stratified squamous epithelium
- Stomach, small intestine and large intestine are simple columnar |
|
Mucosa Components - Villi
|
Small mucosal projections that increase surface area
|
|
Mucosa Components - Lamina Propria
|
areolar tissue containing: blood vessels, sensory nerve endings, lymphatic vessels, smooth muscle cells, lymphoid tissue, and some mucus glands
|
|
Mucosa Components - Muscularis mucosae
|
- two layers of smooth muscle (inner circular, outer longitudinal)
- Alter the shape of the lumen and move plicae circularis and villi |
|
Plicae Circularis
|
permanent transverse folds in intestinal lining
|
|
Submucosa Components
|
- Submucosal glands: secretions carried to lumen by ducts
- Submucosal plexus: nerve network innervating mucosa and submucosa. Contains: sensory neurons, autonomic nerve fibers |
|
Muscularis Externa Components
|
- 2 muscle layers: inner circular, outer longitudinal
- Myenteric Plexus: network of sensory neurons and autonomic neurons (between two muscle layers). Works with submucosal plexus to coordinate local control of digestive activity |
|
Smooth muscle
|
- Found in most organs of the body
- Forms sheets, bundles or sheaths around other tissue - Lacks myofibrils and sarcomeres (no striations=smooth appearance) - Contraction produces shortening=corkscrew movement |
|
What does smooth muscle do in the digestive tract?
|
Regulates movement along digestive tract (circular and longitudinal layers)
|
|
Smooth muscle characteristics - Plasticity
|
can adapt to various lengths and can still contract, important for digestive tract and other organs that change size and shape
|
|
Smooth muscle characteristics - smooth muscle tone
|
normal background activity and tension due to various stimulations
|
|
Type of digestive movement - Peristalsis
|
waves of muscle contraction that propel bolus (moist compact mass of food) through digestive tract
- circular muscle contracts behind bolus - not for digestion/breakdown, mainly for movement |
|
Type of digestive movement - Segmentation
|
- cycles of contraction that churn and fragment bolus
- occurs in many areas of the small intestine and some areas of the large intestine -"breaking down" of food |
|
Control of digestive system - local factors
|
primary stimulus for digestive activities
- Ex. pH, physical distortion, presence of chemicals |
|
Control of digestive system - neural control mechanisms
|
-short reflexes: myenteric plexus neuron response to local factors
long reflexes: interneurons and motor neurons of CNS generally controlling movement from one digestive tract region to another (Synapse with neurons in myenteric plexus) |
|
Control of digestive system - hormonal control mechanisms
|
- peptides produced by enteroendocrine cells within epithelium of digestive tract
- at least 18 hormones |
|
Oral Cavity
|
- Lined by oral mucosa (stratified squamous)
- Keratinized in areas exposed to severe abrasion - Nutrients NOT absorbed here - Digestion of lipids and carbs start here |
|
Oral Cavity Boundaries - Superior
|
- Hard Palate
- Soft Palate |
|
Oral Cavity Boundaries - Anterior and Lateral
|
- Cheeks (mucosa lined, adipose and buccinator muscle within)
- Labia (lips), vestibule (space between teeth and lips), labial frenulum (attachment to gums) - Body of tongue |
|
Oral Cavity Boundaries - Posterior
|
- uvula (prevents food from entering the pharynx)
- palatine tonsils (oropharynx) - root of tongue (marked by circumvallate papillae) - lingual tonsil (base of tongue) |
|
Oral Cavity Boundaries - Inferior
|
- tongue: lingual frenulum (floor of mouth), secretes: water, mucins, enzyme (lingual lipase=lipid digestion)
- Geniohyoid and mylohyoid muscle (support) |
|
Oral cavity structures and organs
|
- pharyngeal arches: sides of uvula
- fauces: connection between oral cavity and oropharynx - gingivae: gums, border each tooth - salivary glands - teeth |
|
Tooth regions
|
- crown: projects into oral cavity
- neck: boundary between crown and root - root: fits into bony cavity or alveolus |
|
Tooth components
|
- enamel: hard surface layer (calcium phosphate)
- dentin: bulk of tooth matrix below enamel - periodontal ligament: create gomphosis articulation between tooth dentin and alveolar bone |
|
Tooth types
|
- Incisors
- cuspids - bicuspids - molars |
|
Tooth type: incisors
|
- blade shaped with single root
- clipping and cutting |
|
Tooth type: cuspids
|
- canines, conical with single root
- tearing and slashing |
|
Tooth type: bicuspids
|
- premolars, flat crowns, 1-2 roots
- crushing, grinding or mashing |
|
Tooth type: molars
|
- large flat crowns, 3+ roots
- crushing or grinding |
|
Pharynx - segments
|
- nasopharynx
- oropharynx - laryngopharynx |
|
Esophagus - Location
|
- posterior to cricoid cartilage
- descends posterior to trachea - passes through esophageal hiatus in diaphragm to reach stomach |
|
Esophagus - sphincters
|
- upper esophageal sphincter (prevents air entering)
- lower esophageal sphincter (prevents backflow of stomach contents |
|
Esophagus - structural characteristics
|
- mucosa and submucosa form large folds that keep lumen closed unless swallowing is occurring (non keratinized stratified squamous)
- muscularis externa: superior 1/3 is skeletal muscle, middle 1/3 is mix of skeletal and smooth, inferior 1/3 is smooth muscle - no serosa: adventia anchors esophagus to posterior body wall |
|
Deglutition
|
- Swallowing
- initiated voluntarily, proceeds automatically |
|
Phases of deglutition
|
- Buccal phase
- Pharyngeal phase - Esophageal phase |
|
Phases of deglutition - buccal phase
|
- voluntary
- formation of bolus and movement to oropharynx |
|
Phases of deglutition - pharyngeal phase
|
- mainly involuntary
- coordinated movement by medulla oblongata to move bolus down to esophagus |
|
Phases of deglutition - esophageal phase
|
- mainly involuntary
- pushed to stomach by peristalic waves - Dry bolus may require secondary peristalic waves |
|
Peritoneal cavity
|
- encloses stomach and most of intestine
- lined with serous peritoneum (parietal and visceral peritoneum, secretes peritoneal fluid to lubricate organs) |
|
Accumulation of peritoneal fluid
|
ascites - abdominal swelling
|
|
Dorsal and Ventral Mesenteries
|
- connective tissue
- function: provide support and carry vessels and nerves - during development two mesenteries exist and develop into other adult connections |
|
Dorsal mesentery becomes:
|
- Greater omentum: connects stomach to intestines
- mesentery proper: small intestine with body wall - mesocolon: large intestine to body wall |
|
Ventral mesentery becomes:
|
- lesser omentum: connects stomach to liver
- falciform ligament: liver to anterior body wall |
|
Stomach - appearance
|
shape is highly variable depending on contents
|
|
Stomach - regions
|
- fundus: superior to esophageal connection
- cardia: within 3 cm of gastroesophageal junction (secretes mucus to protect esophagus from acid/enzymes) - body: largest region - pyloris: sharp curve of "J" leading to small intestine |
|
Stomach structural characteristics - lesser curvature
|
medial surface
|
|
Stomach structural characteristics - greater curvature
|
lateral and inferior surface
|
|
Stomach structural characteristics - rugae
|
mucosal wrinkles that flatten when stomach fills
|
|
Stomach structural characteristics - additional muscle
|
- Oblique muscle layer - in addition to circular and longitudinal in muscularis externa
- assists in mixing and churning |
|
Pyloric (Stomach) structures
|
- pyloric antrum: portion connected to stomach body
- pyloric canal: empties into small intestine - pyloric sphincter: smooth muscle band regulating release of chyme into duodenum |
|
Chyme
|
food, saliva and gastric gland secretions
|
|
Stomach wall layers
|
- mucosa: simple columnar, produces alkaline mucus to protect epithelial cells from acids and enzymes (typical cell lives 3-7 days)
- submucosa - muscularis externa: oblique, circular, longitudinal - serosa |
|
Gastric glands
|
- secrete most of the acids and enzymes enabling gastric digestion
- open to stomach lumen through gastric pits |
|
Gastric gland cell types
|
- parietal cells
- chief cells - G Cells (enteroendocrine cells) |
|
Parietal cells secrete:
|
- intrinsic factor: aids B12 absorption
- HCL: activates pepsinogen |
|
Chief cells secrete:
|
- Pepsinogin: activates in acid (HCL) to become pepsin
-Pepsin=active proteolytic enzyme (protein digesting) |
|
G Cells (enteroendocrine cells)
|
produce a variety of hormones (Gastrin)
|
|
Intestinal structures that add surface area to increase absorption
|
- plicae circularis: permanent transverse folds, mostly in jejunum
- intestinal villi: finger like projections of mucosa - microvili (brush border): cell membrane extensions on simple columnar cells lining villi surfaces |
|
Where are intestinal glands located?
|
base of villi
|
|
Villi - internal structures
|
- extensive capillary bed to absorb nutrients
- lymphatic capillary (lacteal) to transport materials to big for blood capillaries - smooth muscle that squeezes lacteal and moves villi - brush border increases surface area and contains enzymes to digest nutrients |
|
Small intestine characteristics
|
- plays key roll in digestion and absorption
- 90% of nutrient absorption - 3 regions: duodenum, jejunum, ileum |
|
Duodenum
|
- receives chyme from stomach and digestive secretions from liver, gallbladder, pancreas
- mostly retroperitoneal - few plicae circularis and small villi - many duodenal glands secreting mucus - main function is to neutralize acidic chyme - coordinates gastric activity and digestive secretion according to arriving chyme characteristics (hormones) |
|
Jejunum
|
- in peritoneal cavity
- numerous plicae circularis and abundant, long villi - majority of chemical absorption occurs in jejunum |
|
Ilium
|
- final segment of small intestine
- few plicae circularis, stumpy vili - submucosa contains aggregated lymphoid nodules - controls material flow into cecum of large intestine |
|
Major hormones that regulate digestive activities
|
-Gastrin (only one not exclusively produced by the duodenum)
- secretin - gastric inhibitory peptide (GIP) - cholecystokinin (CCK) - vasoactive intestinal peptide (VIP) |
|
Gastrin
|
-only hormone that speeds up stomach activity
- secreted by G cells by the pyloric antrum and enteroendocrine cells of duodenum - stimulated by food presence in the stomach and duodenum (esp. high protein) - Increases production of gastric acids (HCL) and enzymes (pepsinogen) |
|
Secretin
|
- released by duodenum upon arrival of chyme
- increases secretion of bile from liver and buffers from pancreas - decreases stomach activity and secretory rates (acids/enzymes) |
|
Gastric Inhibitory Peptide (GIP)
|
- released by duodenum when fats and carbohydrates (esp. glucose) enter small intestine
- inhibits gastric (stomach) activity while increasing insulin release - stimulates duodenal glands, lipid synthesis in adipose, skeletal muscle glucose use |
|
How are fatty acids stored?
|
Tryglycerides
|
|
Cholecystokinin (CCK)
|
- secreted by duodenum when chyme arrives (esp. high lipid content and partially digested proteins)
- Increase enzyme production and secretion from pancreas - Increase release of bile from gallbladder - inhibits gastric activity and may reduce hunger sensation in CNS |
|
Vasoactive Intestinal Peptide (VIP)
|
- released by duodenum
- stimulate secretion of intestinal glands - dilates regional capillaries (to increase nutrient absorption) - inhibits gastric acid (HCL) production |
|
Phases of gastric secretion
|
- cephalic phase
- gastric phase - intestinal phase |
|
Gastric secretion - cephalic phase
|
- Think about food
- begins with sensations or thoughts about food - CNS initiates preparation for arrival of food at stomach (parasympathetic impulse down vagus nerve) - gastric juice secretions increase |
|
Gastric secretion - gastric phase
|
- get food in stomach
- begins with stimuli as food arrives in stomach: distension of stomach, increase in gastric content pH, presence of undigested materials (esp. proteins and peptides) in stomach - increased gastrin secretion - increased secretion by parietal and chief cells - longest phase |
|
Gastric secretion - intestinal phase
|
- empty stomach into intestine
- begins when chyme enters duodenum - initiation of enterogastric reflex (inhibits gastrin production=decrease in gastric motility and secretion) - stimulates contraction of pyloric sphincter decreasing chyme release into duodenum - increase mucus production in duodenum |
|
Large intestine - major functions during mass movement (peristalsis)
|
- reabsorption of water and compaction of contents into feces
- absorption of vitamins liberated by bacterial action - storage of feces prior to defication |
|
Large Intestine - segments
|
- cecum
- colon - rectum |
|
Large Intestine - cecum
|
- expanded pouch at beginning colon
- begins compaction - contains ileocecal valve - has attached appendix |
|
What two organs does the ileocecal valve connect?
|
- ilium (sm. intestine)
- cecum (lg. intestine) |
|
Inflammation of appendix
|
appendicitis
|
|
What is a colic flexure?
|
bend in the colon
|
|
Large Intestine - colon
|
- ascending: along right margin of peritoneal cavity from cecum to right colic flexure
- transverse: across abdomen from right to left colic flexure - descending: along left margin of peritoneal cavity from left colic flexure to sigmoid flexure - sigmoid: "s" shaped last segment, empties into rectum |
|
Large Intestine - rectum
|
- expandable for temporary feces storage
- fecal matter within rectum triggers defecation urge |
|
Large Intestine structure - taeniae coli
|
- 3 longitudinal muscle bands along outer colon surface (corresponds to muscularis externa)
|
|
Large Intestine structure - Haustra
|
- pouches along colon wall
- allow for expansion and elongation of colon |
|
Large Intestine structure - fatty appendices
|
- teardrop shaped fat sacs attached to serosa
|
|
Large intestine vs. small intestine
|
Large intestine:
- diameter is larger and wall is thinner - lack of villi - abundance of mucus cells (mucus provides lubrication for drier and more compact fecal material) - no digestive enzymes produces |
|
Function of large Intestine
|
- 10% of overall absorption
- absorption of biotin, potassium and B5 (from bacterial activity) |
|
Composition of ejected feces
|
- 75% water
- 5% bacteria - 20% indigestible material |
|
Anal canal
|
- distal portion of rectum
- longitudinal folds (=anal columns) - epithelium transitions from columnar to stratified squamous - large network of veins in the wall - Internal anal sphincter - external anal sphincter - anus (exit of anal canal) stratified epithelium becomes keratinized |
|
Internal anal sphincter
|
- inner circular smooth muscle
- involuntary |
|
External anal sphincter
|
- outer smooth muscle
- voluntary |
|
Defecation reflexes
|
- begins with distension of rectum wall after arrival of feces
- involves 2 positive feedback loops: long reflex, short reflex |
|
Defecation - long reflex
|
- covers greater area
- coordinated by sacral parasympathetic system - stimulates mass movement of feces toward rectum from descending and sigmoid colon |
|
Defecation - short reflex
|
- regional
- stimulation of myenteric plexus to move feces in sigmoid colon and rectum |
|
Accessory digestive organs - salivary glands
|
- produce saliva with mucins and enzymes
- secrete through ducts in oral cavity - parasympathetic stimulation increases salivary secretion - 3 pairs of salivary glands: sublingual, submandibular, parotid |
|
What types of cells do salivary glands consist of, and what do they secrete?
|
- mucus cells, secrete: mucins, water and buffers
- serous cells: secrete: salivary amylase, lysozymes and IgA antibodies |
|
Sublingual salivary glands
|
- located under the tongue
- secrete into sublingual ducts |
|
Submandibular salivary glands
|
- located in mandibular groove
- secrete into submandibular ducts |
|
Parotid salivary glands
|
- located inferior to zygomatic arch
- secrete into parotid duct |
|
Accessory digestive organs - gallbladder
|
- Stores and concentrates bile
- 3 regions: fundus, body, neck - drained by cystic duct (merges with right and left common hepatic ducts from the liver to become common bile duct) - bile released at mealtime into duodenum when hepatopancreatic sphincter is relaxed (under control from CCK) |
|
Bile
|
- produced by liver
- stored in pancreas - break lipid droplets apart (emulsification) |
|
Hepatopancreatic sphincter
|
- encircles the lumen of the common bile duct, pancreatic duct and duodenal ampulla
- resting tension in the sphincter prevents bile flow into the duodenum except at mealtimes |
|
Accessory digestive organs - Pancreas
|
- Exocrine cells secrete buffers and digestive enzymes
- Located posterior to stomach - retroperitoneal - 3 parts: head, body and tail - pancreatic duct - pancreatic lobules - pancreatic acini - pancreatic islets (endocrine function) |
|
Where is the pancreatic head located?
|
lies next to duodenum
|
|
Pancreatic duct
|
meets common duct at duodenal papilla and drains pancreatic juice (water, solutes, enzymes) into duodenum
|
|
Pancreatic acini
|
- produce enzymes
- organizational units made from pancreatic acinar cells |
|
Major pancreatic enzymes
|
- pancreatic alpha-amylase: carbohydrates
- pancreatic lipase: lipids - nucleases: genetic material (RNA, DNA) - proteolytic enzymes: proteins |
|
Accessory digestive organs - liver
|
- largest visceral organ
- 4 lobes: - left lobe - right lobe (separated from left lobe by falciform ligament) - caudate lobe (separated from left lobe by inferior vena cava) - quadrate lobe (between left lobe and gallbladder) |
|
Liver - associated structures
|
- gallbladder: temporarily stores bile produced by liver
- common bile duct: carries bile from liver and gallbladder to duodenum - porta hepatis: entry point for blood vessels and other structures from lesser ommentum |
|
Liver lobules
|
- hexagonal in shape
- separated by interlobular septa - portal area or triad at each corner - composed of liver cells (hepatocytes) |
|
Liver lobules - triad consists of
|
- branch of portal vein
- branch of hepatic artery - branch of bile duct |
|
Liver cells (hepatocytes)
|
- form plates radiating from lobule center (spokes of wheel)
- plates separated by liver sinusoids (blood vessels) - regulate solute and nutrient levels - secretes bile that drains into bile canaliculi then bile ductules then bile ducts of portal triad |
|
Liver sinusoids
|
- drains into central vein (center of lobule)
- contains phagocytic kupffer cells |
|
Primary functions of the liver
|
- synthesis and secretion of bile
- storage of glycogen and lipid reserves - maintenance of normal concentrations of glucose, amino acids and fatty acids in the blood stream - synthesis and interconversion of nutrient types (carbohydrates to lipids) especially with protein - synthesis and release of cholesterol bound to transport proteins - inactivation of toxins (de-toxification) |
|
Why is an acidic environment important in the stomach?
|
- The stomach is acidic in order to kill any bacteria that enter the stomach.
- The stomach has to maintain its acidity for the enzyme pepsin (protein digesting) to function. |
|
Pathway of blood through the liver and back to circulation
|
- blood enters the liver sinusoids from small branches of the hepatic vein and hepatic artery
- as blood flows through sinusoids adjacent hepatocytes regulate solute and nutrition levels - the central vein collects blood from sinusoids - central veins of all the lobules merge to form the hepatic veins - hepatic veins empty into the inferior vena cava |