Exam 5 (Digestive System) Flashcards
GI Tract
aka alimentary canal
def: muscular tube from oral to anus. includes oral cavity, pharynx, esophagus, stomach, small & large intestine
Path of food from mouth to anus
oral cavity ->pharynx -> esophaus -> stomach -> pyloric sphincter -> duodenum -> jejunum -> ilium -> ileolcecal valve -> large intestine -> cecum -> ascending colon -> transverse colon -> descending colon -> sigmoid colon -> rectum -> anus
Visceral Peritoneum vs Parietal Peritoneum
Visceral: aka serosa; covers organs
Parietal: lines inner surface of abdominal cavity
Peritoneal Fluid
between visceral and parietal peritoneum; provides lubrication & reduces friction
Functions of Digestive System!!!!!
- Ingestion: materials enter GI tract
- Propulsion: movement of ingested food along GI tract
- Mechanical chewing: chewing food
- Secretion: release of hormones, enzymes, acids, buffers, & salts by GI epithelium & glands
5.Chemical Digestion: chemical breakdown of food by enzymes & acids - Absorption: movement of nutrients across GI epithelium into blood & lymphatic vessel
- Defecation: excretion of indigestible materials & metabolic wastes via feces
Mesenteries
sheet of visceral peritoneum that connect visceral & parietal peritoneum & stabilize & protect digestive organs
Lesser Omentum
keep stomach in place
Greater Omentum
protects abdominal organs
Mesentery Proper
stabilizes small intestines
Falciform Ligament
stabilizes liver
Mesocolon
stabilizes large intestine
Layers of Digestive Tract
- Mucosa
- Submucosa
- Muscularis Externa (circular & longitudinal)
- Serosa (visceral peritoneum)
Mucosa
location: innermost layer
component: epithelium (thin layer around lumen), lamina propria (areolar connective tissue), muscularis mucosae (thin layer of smooth muscle in mucosa)
Submucosa
def: made of dense connective tissue & contains vessels, nerves, and glans
*submucosa gland: secrete buffer & enzymes
Muscularis Externa
def: two layers of smooth muscle: inner circular & outer longitudinal layers
*responsible for propulsion
Serosa
aka visceral peritoneum
def: simple squamous epithelium & lose connective tissue form outermost layer
Peristalsis vs Segmentation
Peristalsis: muscle contraction that propel food forward
Segmentation: mechanical processing by mixing in intestine. No forward movement.
Local Factors that Affect Digestive Functions
Ex: pH, volume, or chemical composition of the intestinal contents.
Some of these local factors have a direct effect on local digestive activities: stretching of the intestinal wall can stimulate localized contractions of smooth muscles: histamine stimulates the secretion of acid in stomach
Short vs Long Reflex
Short: local neural control by enteric nervous system = regulates motility & secretion independently of CNS
Long: motility & secretions regulated by ANS- sympathetic inhibits & parasympathetic stimulates
Anatomy of Oral Cavity
- lined w/ oral mucosa that’s highly vascularized
-contains accessory organs: teeth, tongue & salivary glands (which turn ingested food into moist, chewed mass = bolus)
Function of Oral Cavity
-Sensory analysis (tongue)
-Mechanical digestion (tongue & teeth)
-Lubrication by mucus & saliva (salivary glands)
-Initial chemical digestion of carbohydrates & lipids (salivary glands)
-NO ABSORPTION OF NUTRIENTS
Function of Tongue
-Mechanical processing: compression, abrasion & distortion
-Assist w/ chewing & swallowing
-Sensory analysis: taste, temp, touch
-Secrete lingual lipase: enzyme that digests triglycerides into glyceride & fatty acids
Types of Teeth
-Incisors (front teeth)
-Canines (vampire teeth)
-Premolars (after incisors before molar)
-Molar (back teeth)
Function of Teeth
Mastication: mechanical digestion which increase overall surface area of food, allowing for better chemical digestion
Components of Saliva
def: fluid containing water, electrolytes, enzyme, mucus, & other solutes (salivary amylase- enzyme digests starch into smaller sugars
Functions of Saliva
-Moisten & lubricate oral cavity & contents
-Dissolve chemicals that stimulate taste receptors & provide sensory info
-Initiate chemical digestion
-Prevent bacterial growth
Types of Salivary Glands
- Parotid Glands: 30% of saliva; location- by ears // secrete watery, serous cells w/ enzymes
- Sublingual Glands: secrete least saliva; location- floor of mouth // mucous, lubricating saliva
- Submandibular Glands: secrete most saliva; location- the mandible /// combination of other 2
Pharynx
shared passageway w/ respiratory system
Esophagus
uses muscle peristalsis to move bolus
Sphincters (2)
- upper esophageal sphincter: entrance of esophagus; what opens to let food through by peristalsis contraction
- gastroesophageal sphincter: end of esophagus; allow bolus to enter stomach & prevent acid to go into esophagus
*function: prevent backflow
Phases of swallowing
- Voluntary (Oral) Phase: food is mouth; tongue pushes bolus into oropharynx
- Pharyngeal Phase: involuntary; bolus enters oropharynx; epiglottis seal off nasopharynx & larynx. Respiratory centers are inhibited by swallowing reflex
- Esophageal Reflex: involuntary; food traveling down esophagus by peristaltic wave toward stomach
Stomach Anatomy
-lesser & greater curvature
-regions:
*cardia, fondus, body, pyloric
-gastroesophageal (entrance) & pyloric sphincters (exit) toward small intestine
-rugae: folds = allow stomach to expand
Function of Stomach
-Storage of food: rugae = expansion
-Mechanical digestion: churning makes bolus into chyme (viscous acidic mix of partially digested food)
-Chemical digestion
-Produce of intrinsic factory (necessary for vitamin B12 absorption in small intestine)
-NO ABSORPTION OF NUTRIENTS
Gastric Pits vs Gastric Glands
Gastric Pits: in-foldings of inner surface of stomach mucosa
Gastric Glands: located below gastric pits, secrete hormones & gastric juice
Chief Cells
part of gastric glands
secrete: inactive pepsinogen
function: activated to pepsin by HCl in lumen
Parietal Cells
secrete: intrinsic factor & HCl
Goblet Cells & Mucous Neck Cells
secrete: mucus
function: protects lining of stomach
G Cells
endocrine cells
secrete: hormone gastric
function: stimulate stomach secretions & contractions
Somatostatin
inhibits gastrin release = decrease stomach stimulation & gastric juices
Function of stomach pH
- Kill microorganism
- Digests plant cell walls & connective tissues in meat
- Activate pepsinogen into pepsin
- Optimal pH for digestive enzymes (acidic pH)
Phases of Gastric Activity
- Cephalic Phase
- Gastric Phase
- Intestinal Phase
Cephalic Phase
role: stomach preparing for food
1. sight, smell, taste, or thought of food
2. gastrin secreted & somatostatin inhibited
3. results in increase stomach secretion
head, thinking about food and preparing to eat, stomach starts preparing by secreting gastric juice & churning, begin salivating
Gastric Phase
role: bolus enters stomach & stretches it
1. increase gastrin
2. if pH drops too much = somatostatin is released
food enters stomach, stomach stretches, increase secretion & motilitiy.
Intestinal Phase
role: chyme enters small intestine
1. duodenum increases mucus to protect from acid in chyme
2. secretes gastrin if presence of incompletely digested proteins
3. secretin, CCK, GIP released to inhibit gastric secretion & stimulate pancreatic juice
food enters small intestine, food released slowly
Parts of Small Intestine
duodenum, jejunum, ileum
Small Intestine
folds increase surface area for absorption. Large to small: plicae, villi, microvilli
Why does duodenum have mucous glands?
neutralize acid & mix chyme w/ secretion from pancreas & liver/gallbladder
Function of Small Intestine
-propel food forward by peristalsis & segmentation
-completion of chemical digestion by pancreatic & intestinal brush border enzymes & bile from liver
*most absorption takes place in small intestine
Brush Border
formed by microvilli on surface of epithelial cells
release enzymes:
-lactase = digest lactose
-maltase = digest maltose
-sucrase = digest sucrose
release enzymes that activate inactive enzymes from pancreas
Exocrine Cells
in Pancreas
-secrete: pancreatic juice
-where: into small intestine
Pancreatic juice
mixture of ensymes & buffers
ph 7.5-8.8
why: netrualize acid in chyme
Liver Lobules
-hexagonal lobules: center has middle vein and vessels in corners
-sinusoids: lead toward middle vein
-hepatocytes: main liver cells
-kupffer cells: liver immune cells
Function of Liver!!! (know 5)
- Bile production
- Nutrient Metabolism
- Detoxification
- Excretion
- Phagocytosis & Antigen Presentation
- Synthesis of plasma proteins
- Absorption & recycling of old hormones & antibodies
Types of Lipoproteins!!!!
-Chylomicrons: contain dietary lipids (lipds from diet) / made in digestive tract and go to liver
-VLDLs: made by liver and go to tissues / contain cholesterol & lipids
-LDLs: made by liver and go to tissues/ contain mostly cholesterol
-HDLs: made by tissue cells and go to liver / contain cholesterol
Bile Contents & Functions
Contents: water, (lipids) cholesterol, bile salts, bile waste
Function: emulsifies lipids: breaks lipids into smaller droplets = easier to mix w/ water = enzymes have better access
allow for excretion of toxic waste
Large Intestine Anatomy
Cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum
ileolcecal valve
between ilium (last portion of small intestine) and cecum (beginning portion of large intestine)
haustra & taeniae coli
haustra: pouches in surface of large intestine
taeniae coli: structure that creates haustra
veniform appendix & anal sphincter
veniform: lymphoid organ protruding from cecum
internal involuntary and external voluntary sphincters
Function of Large Instestine:
-absorb water, electrolytes, bicarbonate & bile salts
-absorb vitamins generated by bacteria
-bacteria inside break down undigested materials
-produce & store fecal material
Digestion & absorption of carbs, proteins, & lipids
Carbs: large polysaccharides to disaccharides and monosaccharides and absorb into surface of small intestine into BLOOD capillaries
Proteins: broken into amino acids and absorbed into surface of small intestine into BLOOD capillaries
Lipids: broken into fatty acids and absorbed into small intestine into LYMPHATIC capillaries
gallbladder
where bile is stored and concentrated.
gallstone= overly concentrated bile
