Chapter 23: Digestion Flashcards
4 main functions of the Digestive Tract
- Take in food
- Break it down into nutrients
- Absorb molecules into bloodstream
- Rid body of indigestible remains
What are the two main groups of the digestive system
Alimentary Canal
Accessory Organs
What is the alimentary canal?
GI Tract/GUT
Continuous muscular tube from mouth to anus
What is the function of the alimentary canal?
- Digest Food
2. Absorb fragments through lining into blood
What is the order of the alimentary canal parts?
Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Anus
What is the accessory digestive group?
Organs and Glands
Teeth
Tongue
Gall Bladder
Digestive Glands
What are the digestive glands?
Salivary Glands
Liver
Pancreas
What are the 6 essential activities of the GI tract?
Ingestion Propulsion Mechanical Breakdown Digestion Absorption Defecation
What is ingestion?
process of taking in food, water or other substance by swallowing or absorbing
What is propulsion?
Movement of food via waves of contraction and relaxation
What is mechanical breakdown?
Chewing, mixing food with saliva, churning food, segentation
What is digestion?
Catabolic steps that involve enzyme breakdown of complex food molecules
What is absorption?
Passage of digested fragments from lumen of GI tract into blood/lymph
What is defecation?
elimination of indigestible substances via anus
What are the two types of propulsive movements of digestion?
Peristalsis
Segmentation
What is peristalsis?
Forward movement down the tube
What is segmentation?
mixing forward and backyard movement, some propulsion may occur
What makes up the digestive tract membrane?
Visceral peritoneum
Parietal peritoneum
Peritoneal fluid
What is visceral peritoneum?
Membrane on external surface of most digestive organs
What is parietal peritoneum?
Membrane that lines body wall
What is peritoneal fluid?
Found in digestive membrane, lubricates mobile organs
What are the 4 main layers of the GI tract, from outermost to innermost?
Serosa
Muscularis Externa
Submucosa
Mucosa
What does the serosa contain?
Outer: Epithelium
Inner: Connective Tissue
What does the muscularis externa contain?
Outer: Longitudal layer
Inner: circular layer
What is the role of the muscularis externa?
Segmentation and peristalsis
What does the submucosa contain?
Blood & lymphatic vessels
lymphoid follicles
submucosal nerve plexus
What does the mucosa contain?
epithelial lining
lamina propria
muscularsis mucosae
What is the function of the mucosa?
- Secrete mucus, digestive enzymes, and hormones
- Absorb end products of digestion into blood
- protect against infectious disease
What regulates digestive activity?
Mechanical and chemical stimuli found in walls of GI tract
What do digestive stimuli respond to?
stretch and changes in osmolarity and pH
What are the EFFECTORS of digestive activty?
Smooth Muscle
Glands
Who controls digestive activty?
Neurons and hormones
What are the digestive nervous systems?
Intrinsic (enteric)
Extrinsic (Autonomic)
What is another name for the oral cavity?
Buccal cavity
What are the boundaries of the oral cavity?
Lips, cheeks, palate, tongue
What is the anterior opening of the oral cavity?
oral oriface
What is the oral cavity lined with? Why?
Stratified squamous epithelium for protection
What are the locations of the 3 frenulums?
Superior labial frenulum
Lingual Frenulum
Inferior labial frenulum
What forms the hard palate?
palentine bones
What forms the soft palate?
skeletal muscle
What is the for the little holes under the tongue?
Submandibular duct and sublingual opening
What are the functions of the tongue?
Gripping
Formation of bolus
Initiation of swallowing, speech and taste
What are the 4 surface bears papillae?
Filliform papillae
Fungiform papillae
Vallate papillae
foliate papillae
What is the function of the filliform papillae?
1) Gives tongue roughness to provide friction - ie. licking ice cream
2) only papillae that does not contain taste buds, 3) gives tongue white appearance
Describe the fungiform papillae
Mushroom shaped and scattered widely
- Vascular core causes reddish appearance
- tastebuds
Vallate (circumvallate) papillae
V shape row in back of tongue
taste buds
Folliate papillae
taste buds
lateral aspects of posterior tongue
What are the locations of the 3 salivary glands?
Parotid
Submandibular
Sublingual
What are the functions of saliva?
Cleanse Mouth
Dissolve food chemicals for taste
Moisten food, compact into bolus
Begin breakdown of starch with enzyme amylase
What are the two types of secretions in the salivary glands/
Watery and Mucous
What type of cells produce watery saliva?
Serous cells
The salivary glands are activated by which autonomic nervous system?
parasympathetic
The salivary glands are inhibited by which autonomic nervous system?
sympathetic
How are teeth classified?
Shape
What are the 4 teeth shape? What are their roles?
Incisors - cutting
Canines- tearing or piercing
Premolars - grind or crush
Molars - best grinders
How many deciduous teeth do we have? What happens to their roots?
20
Roots are reabsorbed
How many adult teeth do we have?
32
What are the roles of the oropharynx and laryngopharnyx?
Allow passage of food, fluids and air
What types of cells make up the oropharynx and larygngopharnyx?
Stratified squamous epithelium
What makes up the external layer of the oropharynx and larygngopharnyx?
skeletal muscle
Where does the esophagus begin and end?
larygngopharnyx to the stomach
Where does the esophagus pierce the stomach?
Esophageal hiatus
Where does the esophagus enter the stomach?
cardial orifice
What is mastication?
chewing
How does mechanical digestion occur?
mastication
Who is responsible for chemical digestion?
salivary amylase
What is deglutition?
swallowing
How is propulsion accomplsihed?
deglutition
What are the 2 major phases of deglutinition?
Buccal Phase
Pharyngeal-Esophageal Phase
What is the Buccal Phase?
Voluntary contraction of the tongue, pushes food into oropharynx
What is the esophageal phase?
involuntary
How does peristalsis move food into the stomach?
Moves food down the esophagus, entering the stomach at the cardia
What must relax in order for food to enter the stomach?
Lower esophageal sphincter.
What are the 4 areas of the stomach?
Cardia
Fundus
Body
Pylorus
What types of cells are found in the gastric pits of the stomach?
Mucous neck cells
Parietal Cells
What do parietal cells make?
HCl and intrinsic factor
Why is intrinsic factor necessary?
It’s a glycoprotein required for absorption of B12 into the small intestine
What does HCl activate?
Activates pepsinogen to make pepsin
Who makes pepsinogen?
Chief Cells
What do enteroendocrine cells make?
hormones and paracrines
What is the mucosal barrier? Why is the mucosal barrier significant?
Thick layer of bicarbonate-rich mucus and tight junctions between epithelial cells, prevents juice from seeping underneath tissue
2) Protects from harsh digestive materials
What digestive processes does the stomach participate in?
chemical and mechanical digestion
The stomach acts as what for food?
holding area
What does the stomach deliver to the small intestine?
chyme
What does the stomach us HCl for?
Denature proteins
How does the stomach digest protein?
pepsin
What does the stomach absorb?
water, lipids, alcohol
What does the stomach help produce?
intrinsic factor
What is a lack of intrinsic factor?
Pernicious anemia
How do peristaltic waves move? how Fast?
Toward the pylorus at 3 contractions/minute
What is the basic electrical rhythm initated by?
Pacemaker cells
What increases the force of stomach contractions?
Stretch and gastrin
Where are stomach contractions most vigorus?
Pylorus region
How much chyme is delivered to the small intestine at one time?
3 mL
Why are the liver, pancreas and gallbladder considered accessory organs?
They’re not part of the tube, but associated with the small intestine
What does the liver produce? What is it used for?
Production of bile
Bile used to emulsify fat (enhance absorption of fat)
What does the pancreas produce?
1) Enzymes needed to digest chyme
2) Bicarbonate to neutralize stomach acid
What is the role of the gallbaldder?
Store bile
What is the largest gland in the body?
liver
How many lobes does the liver have?
4
What are the hepatocyte functions?
Produce 900 mL bile/day
Process bloodborne nutrients
Store fat soluble vitamins
Detoxification
What is bile made up of?
bile salts
billirubin
What do bile salts assist with?
Fat digestion
What are the fat soluble vitamins?
A,D,E,K
How much of the bile salts are reabsorbed into the liver?
95%
What is the gallbladder?
Thin walled muscular sac on the ventral surface of the liver
What are the functions of the gall bladder?
1) Storage of bile
2) Release of bile via the cystic duct into the bile duct
What are the pancreas’ endocrine functions?
Insulin and pancreatic juice
What are the pancreas exocrine functions?
Production of pancreatic juice
What do the zymogen granules contain?
digestive enzymes
How much pancreatic juice is produced each day?
1200-1500 mL
What form are enzymes secreted in? Why?
Inactive, protects the cells producing the enzymes from being digestion
What enzymes are secreted in an inactive form?
Trypsinogen
Chrymotripsinogen
Procarboxypeptidase
What converts inactive enzymes to active enzymes?
Enteropeptidase
What are the 3 parts of the small intestine?
Duodenum
Jejunum
Illeum
What is the major roll of the small intestine? Minor roll?
Absorption!
digestion
How long is the duodenum? What 2 ducts enter here? What are the ducts delivering?
25 cm/10in
common vile duct and pancreatic duct
Pancreatic juices
How long is the jejunum?
2.5m/8ft
How long is the illeum? Where does it join the cecum?
12 ft long
Joins cecum at ileocecal valve
What are the modifications to the small intestine?
Increase surface area to enhance opportunities for absorption
What are the small intestine modifications?
Circular folds
Villi
Microvilli
Describe Circular Folds
Permanent folds that force chyme to slowly spiral through lumen, allow for more nutrient absorption
Describe VIlli. What are Lacteals for?
Fingerlike projections of mucosa with core containing dense capillary bed and lymphatic capillary called lacteal
Lacteal for absorption
What are microvilli?
Cytoplasmic extensions called brush border containing brush border enzymes for final stage of digestion
What makes up the large intestine?
Cecum
COlon
Rectum
Anal Canal
What is the cecum?
First section, a blind sac with appendix attached to it
What are the 4 parts of the colon?
Ascending
Transverse
Descending
Sigmoid Colon
Where is the ascending cavity?
Up right abdominal cavity to level of right kidney
Where is the transverse colon?
Across abdominal cavity
Where is the descending colon?
travels down left side of adominal cavity
Where is the sigmoid colon?
S-shaped traveling through pelvis
What is the rectum for?
3 valves to stop feces from being passed with gas
What is the anal canal? What are the 2 sphincters
Last segment of large intestine
Internal anal sphincter
External anal sphincter
What type of muscle is the internal anal muscle?
smooth muscle
What type of muscle is the external sphincter?
skeletal muscle
How many species of bacteria are in the large intestine? How does it compare to our own cells?
1000+
Population outnumbers our own cells, 10x1 but much smaller in size
what are the functions of bacteria in the large intestine?
Fermentation
Synthesize vitamins
What is fermentation?
Fermentation of indgestible carbs and mucin, producing irritating acids and gases
What vitamins are synthesized and why?
B and K, needed by liver to produce clotting factors
What immune cells watch for bacterial cells to breach mucosal barrier?
Dendritic and igA
What is the function of the large intestine?
NOT digestion, no food uptake
Propulsion and Defecation main job
Major reclamation of Vitamins (B & K), electrolytes and water
How does defecation occur?
Distension of rectum initiates the defecation reflex via parasympathetic signals. Contraction of rectal muscles expels feces
What are the parasympathetic signals of defecation?
Stimulate sigmoid colon and rectum contraction
Relax internal anal sphincter
What type of control do we have over the anal sphincter?
COnscious
What does digestion do?
Breaks down food into chemical building blocks so that they can be absorbed by small intestine
What type of process is digestion?
Catabolic process that breaks down into monomers
How does absorption occur?
Moving from lumen of the gut into the body
What type of movement does tight junction allow for?
Movement through plasma membrane of enteric cell, not between and then into blood of lacteals (for fat)
Why are carbohydrates digested? How?
Digested to yield monosacharides (single sugar)
1) Salivary analyese
2) Pancreatic analyese
3) Brush Border Enzymes break sections into monosacharides
How is protein digested?
1) Pepsin breaks proteins into large polypeptides
2) Pancreatic enzymes break large polypeptides into small polypeptides and peptides
3) Brush border enzymes break peptides into individual amino acids
4) AA are absorbed
How are fats digested?
1) Emulsified by bile
2) Acted on by pancreatic lipases
3) Absorbed as fatty acids and monoglyceride via diffusion
4) Form chylomicron packages within enteric cells
5) Chylomicrons sent by exotosis out of cell and move into lacteal then to lymphatics and then blood
How are nucleic acids digested?
Broken down by pancreatic ribonuclease and deoxyribonuclease
2) Brush border enzymes break into pentoses, bases and phosphate ions for absorption
How much water is absorbed each day? How does it enter the GI tract? What % is absorbed by small and large intestine?
9 L
Enters as secretions
small intestine 95%
large intestine 5%
What is GERD? What happens in Gerd? What does it result in?
Gastroesophageal reflux disease
Heartburn
Stomach juices enter and irritate esophagus
Results in esophagitis, ulcers and esophageal cancer
What is gastritis?
inflammation by aything breaching stomach’s mucosal barrier
What is a gastric ulcer? What can it cause? What causes it?
Erosion in stomach wall
Can cause bleeding
Caused from bacteria heliobacter pylori and NSAIDs
Vomiting is caused by…
Extreme stretching or by intestinal irritants
What is hepatitis?
Inflammation of the liver
Caused by viruses
Drug toxicity
wild mushrooms
What is cirrhosis? What causes it? How is advanced cirrhosis treated/
Progressive chronic inflammation of liver
Caused by excessive alcohol or virtal hepatitis
Liver transplant for advanced
What are 2 colon problems?
Diverticulosis
Diverticulitis
What is diverticulosis
Presence of diverticula
What is diverticulitis
?
Inflamed diverticula that can be life threatening when ruptured
What is diarrhea?
Watery feces, occurs when colon doesn’t have enough time to absorb water due to irritation by food, bacteria or jostling (marathon runners)
