What are the 6 steps in digestion?
2. Mechanical digestion
4. Chemical digestion
Layers (Tunics) of GI Wall
3. Circular and Longitudinal Smooth Muscle
1. What does this layer face?
2. Made of? Specialized for?
3. Blood supply?
4. What does it consist of? 4
Circular and Longitudinal Smooth Muscle
6. Faces what?
1. Innermost layer (faces lumen)
2. Layer of epithelial cells specialized for absorption and secretion
3. Highly vascularized
4. Consists of collagen, elastin, glands, and blood vessels
Circular and Longitudinal Smooth Muscle
5. Provides motility for GI tract
6. Faces the blood
What enzymes break down food in the mouth?
1. lingual amylase
carb. (step 1)
2. lingual lipase
lipid (step 1)
1. ____muscles and 2.___cranial nerves (600 times/daily)
3. What does the esophageal phase of swallowing begin with?
4. Composition of Saliva→ Secreted by ______ and _______cells
5. What is saliva composed of? 6
-Begins with crico-pharyngeal relaxation
4. serous and mucous
a) 97–99.5% water, slightly acidic
b) lytes—Na+, K+, Cl–, PO4 2–, HCO3–
c) Salivary amylase and lingual lipase
e) Metabolic wastes—urea and uric acid
f) Lysozyme, IgA and a cyanide compound protect against microorganisms
1. Salivary glands produce how much saliva a day?
2. Functions of saliva? 4
1. Salivary glands produce 1 L/day of saliva
-Each gland delivers saliva to mouth through a duct
Functions of saliva
1. Initial digestion of starches and lipids by salivary enzymes
2. Dilution and buffering of ingested foods
3. Lubrication of ingested food to aid its movement
4. Many more functions
Secretions are produced by what? 4
What do secretions add to the lumen of GI tract? 4
Secretions produced by
1. Salivary glands (saliva)
2. Gastric mucosal cells (gastric secretion)
3. Pancreatic exocrine cells (pancreatic secretion)
4. Liver (bile)
Addition of GI tract:
2. Small intestine?
3. Large intestine?
1. Stomach: digestion and break down of food to smaller, absorb-able particles.
2. Small intestine: absorption of nutrients
3. Large intestine: absorption of water
1. What is the stomach specialized for?
2. Holds how much?
3. Gastric juice converts food into semiliquid called what?
4. 4 parts of the stomach?
1. Specialized for accumulation of food
2. Capable of considerable expansion (can hold 2-3L)
3. Gastric juice converts food into semiliquid called chyme
4. 4 Parts
Functions of Stomach
1. Short-term storage reservoir
2. Absorption, digestion and secretion
3. Chemical and enzymatic digestion is initiated, particularly of proteins
4. Liquefaction of food→ chyme
5. Slowly released into the small intestine for further processing
6. The stomach uses pepsin and peptidase (enzymes) to break down proteins
Why is the acidic anvironment of the stomach important?
The acid provides good environment for the enzymes to work in.
What are the Three Phases of Digestion?
1. Cephalic Phase
2. Gastric Phase
3. Intestinal Phase
1. Cephalic Phase: What structures are involved? 4
2. Gastric Phase: What substances are involved? 2
3. Intestinal Phase: What hormone is involved?
Cephalic Phase :
4. vagus nerve
1. hydrochloric acid
1. enterogastrone Hormones secreted in duodenum and lower GI tract.
1. During cephalic and gastric phases, stimulation by vagal nerve fibers causes release of what?
2. Acidic chyme entering duodenum causes the enteroendocrine cells to release what?
3. Whereas fatty, protein rich chyme induces release of what?
4. Where do these two enzymes go next?
1. pancreatic juice and weak contractions of the gallbladder
4. Blood stream
1. Upon reaching the pancreas, cholecystokinin induces the secretion of what?
2. Secretin causes copious secretion of what?
1. enzyme-rich pancreatitis juice
2. bicarbonate-rich pancreatic juice
1. Gastric mucosal cells secrete what?
2. What two substances initiate protein digestion?
3. What is required for absorption of Vit B12?
4. Body of the stomach conatins what kind of glands?
5. Atrum of the stomach conatins what kind of glands?
6. What protects gastric mucosa from HCL?
1. gastric juice
2. HCl and pepsinogen initiate protein digestion
3. Intrinsic factor required for absorption of vitamin B12
4. Body of stomach contains oxyntic glands
5. Antrum of stomach contains pyloric glands
6. Mucus protects gastric mucosa from HCl
1. What are the two types of cells in the body of the stomach?
2. What are the two types of cells in the antrum of the stomach?
1. Parietal cells and Chief cells
2. G cells and Mucous neck cells
1. What do parietal cells secrete? 2
2. What do chief cells secrete? 1
3. G cells secrete what? 1
4. What do mucous neck cells secrete? 3
1. Parietal cells → HCl and Intrinsic Factor
2. Chief cells → Pepsinogen
3. G cells → Gastrin into the circulation
4. Mucous neck cells → Mucus, HCO3-, and Pepsinogen
1. Gastrin: Secreted by G cells in stomach in response to what?
2. Stimuli includes what? 3
3. Gastrin promotes what kind of secretion?
4. Stimulates the growth of what?
5. What is its secretion inhibited by?
-distention of stomach
3. Promotes H+ secretion by gastric parietal cells
4. Stimulates growth of gastric mucosa
5. Low pH in the stomach
Other Functions of GASTRIN HORMONE:
1. Pepsinogen release
2. Increase stomach motility
3. Relax pyloric sphincter
4. Contract LES
Regulation of HCl Secretion
What three hormones are involved in this?
1. ACh is realeased from?
2. Binds to receptors where?
3. Produces what by parietal cells?
4. What blocks muscarinic receptors on parietal cells?
1. Released from vagus nerve
2. Binds to receptors on parietal cells
3. Produces H+ secretion by parietal cells
4. Atropine blocks muscarinic receptors on parietal cells
1. Histamines released from mastlike cells where?
2. Binds to what on parietal cells?
3. Produces what by parietal cells?
4. What block H2 receptors?
1. Released from mastlike cells in gastric mucosa
2. Binds to H2 receptors on parietal cells
3. Produces H+ secretion by parietal cells
4. Cimetidine blocks H2 receptors
1. Released into circulation by what of stomach antrum?
2. Binds to receptors of what cells?
3. Stimulates what?
1. Released into circulation by G cells of stomach antrum
2. Binds to receptors on parietal cells
3. Stimulates H+ secretion
What are the two general processes that cause peptic ulcers?
Impaired host defenses
What things could cause increased damage in the stomach causing a peptic ulcer? 8
What things could cause impaired defenses in the stomach that lead to peptic ulcers? 3
What is segmentation contractions?
1. Circular muscle contracts sending chyme in both directions
2. Intestine then relaxes allowing chyme to merge back together
What is peristalic contractions? 2
1. Longitudinal muscle contracts propeling chyme along small intestine
2. Simultaneously, portion of intestine caudad to bolus relaxes
1. What are the enzymes (2) in the salivary glands and what are their targets (2)?
2. What are the enzymes (2) in the stomach and what are their targets (2)?
3. What are the enzymes (5) in the Pancreas and what are their targets (5)?
4. What are the enzymes (3) in the intestine and what are their targets (3)?
Autonomic Nervous System has an extrinsic and an intrinsic component
1. Extrinsic controls what? 2
2. What is the intrinsic also called?
3. Contained where?
4. Communicates with what?
-Parasympathetic innervation of GI tract
2. Called Enteric Nervous System
3. Contained within wall of GI tract
4. Communicates with Extrinsic component
1. The nervous system of the GI tract regulates what? 3
2. Parasympathetic nerve supply comes from where and provides motor innervation to what?
3. Sympathetic nerve supply comes from the cervical and thoracic sympathetic chain and regulates what? 4
-blood vessel caliber, and the
-activity of striated and smooth muscle.
2. Parasympathetic nerve supply comes from the
-nucleus ambiguus and dorsal motor nucleus of the vagus nerve***** and
-provides motor innervation to the esophageal muscular coat and secretomotor innervation to the glands.
-blood vessel constriction,
-esophageal sphincters contractions,
-relaxation of the muscular wall, and
-increases in glandular and peristaltic activity
Can direct all functions of GI in absence of extrinsic innervation
1. Which functions of the GI system does it control? 3
2. Where does it recieve input from? 2
3. Sends information directly where? 3
-endocrine functions of GI tract
2. Receives input from
-Parasympathetic and sympathetic nervous systems
-Mechanoreceptors and chemoreceptors in mucosa
3. Sends information directly to
1. Gastric mucosa has numerous openings called what?
2. What empties into these?
3. 4 functionally different cell types compose glands?
1. Gastric pits
2. Gastric glands
What is the primary site fo digestion and absorption of nutrients?
What empties into the the duodenum? 2
Bile duct and pancreatic duct
1. Function of the hepatic portal vein?
2. Describe its high blood flow?
Receives major blood supply from hepatic portal vein
1. Brings venous blood rich in nutrients from digestive tract
2. High blood flow - 1350 ml/min to liver sinusoids (1050 ml from the portal vein, 300 ml from hepatic artery) = functional and nutritive blood circulation
Describe the vascular resistance in the liver?
Describe how this changes with cirrhosis?
1. low vascular resistance (small difference between pressures in the portal vein and hepatic vein) -
2. in case of cirrhosis, the vascular resistance increases, blood flow decreases (portal hypertension……………ascites)
1. Hepatocytes are in contact with blood in structures called _________within the liver.
2. These function like ______ ________.
-Arranged to form functional units (lobules)
2. blood capillaries
Overview Of Hepatic
1. Carbohydrate metabolism.
2. Lipid metabolism.
3. Protein metabolism.
4. Removal of drugs and hormones.
5. Excretion/secretion of bilirubin.
6. Synthesis of bile salts.
7. Storage of some compounds.
9. Aids in the synthesis of active vitamin D.
10. Urea formation from ammonium
Steps in food digestion
1- Carbohydrates? 2
2- Proteins? 2
3- Lipids? 2
1- Carbohydrates ---> disaccharides ---> monosaccharides
2- Proteins ---> peptides ---> amino acids
3- Lipids ---> diglycerides ---> monoglycerides and fatty acids
Absorption of carbohydrates
1. In what form are they absorbed?
2. The monomers are carried by transporter molecules across the epithelial cells and into the what?
1. Monosaccharides (mostly glucose) are absorbed
2. blood capillary present in the villus → portal vein → liver
Overview of digestion of Lipids
1. _________of fatty acids to supply energy for other body function
2. Synthesis of large quantities of what? 3
3. Inactivation of ______and their excretion from the body
-cholesterol (80% of cholesterol synthesized in the liver is converted into bile salts),
1. What is Ammonia detoxification disorder and failure of urea formation. Ammonia comes from? 3
2. Hyperammonemia = ?
1. ammonia comes
-from bacterial degradation of nitrogen substances in intestines,
-from intestinal mucosa during glutamine degradation,
-from degradation of amino acids in kidneys and muscles
2. Hepatic encephalopathy = toxic effect of ammonia in the brain
Hyperammonemia = Hepatic encephalopathy = toxic effect of ammonia in the brain. What signs and symptoms will you have?
1. Mental changes (disorientation, sleeping disorders, chaotic speech, personality changes)
2. Motor changes (increased in muscle reactivity, hyperreflexia, tremor)
Endogenous causes of hepatic coma and death? 2
Hepatic coma to death
1. Endogenous =
-viral hepatitis and
-poisoning (hepatic cell disintegration)
2. Exogenous = final status of chronic cirrhosis (ammonia and other toxic substances bypass the liver through the extrahepatic anastomoses)
1. What is bile necessary for?
2. What is it a mixture of? 3
3. What do bile salts do?
1. Necessary for digestion and absorption of lipids in small intestine
2. Mixture of
-bile pigments, and
3. Bile salts emulsify lipids to prepare them for digestion
Bile Secretion and Recycling
1. Produced and secreted where?
2. Stored where?
3. Ejected into the small intestine when what happens?
4. After lipids absorbed, bile salts are re-circulated to liver via what?
5. Extraction of bile salts from the portal blood by what?
1. Produced and secreted by liver
2. Stored in gallbladder
3. Ejected into small intestine when gallbladder contracts
4. After lipids absorbed, bile salts are re-circulated to liver via enterohepatic circulation
5. Extraction of bile salts from the portal blood by hepatocytes
After lipids absorbed, bile salts are re-circulated to liver via enterohepatic circulation
1. Absorption of from where to where?
2. Delivery back to?
1. Absorption of bile salts from ileum into portal circulation
2. Delivery back to liver
Formation Of Bilirubin
1. Formed from?
2. Hb is phagocytosed by what?
3. Iron released is bound to what and transported in the blood?
4. The remainder of the heme group is converted to ________, which is rapidly reduced to_______.
5. What does it then attach to?
2. tissue macrophages (spleen)
4. biliverdin, bilirubin
Secretion of bilirubin into bile by the liver is a classic example of what?
waste and toxic elimination by the liver
Processing of bilirubin by hepatocytes
1. Albumin is removed as unconjugated bilirubin passes through the what?
2. Bilirubin is conjugated with ____________(80%), ________(10%) or a variety of other substances (10%)
Secretion of Conjugated Bilirubin Into Bile
1. Conjugated bilirubin has a _______ solubility?
2. Hepatocytes actively transport conjugated bilirubin into the what?
3. Conjugated bilirubin then enters duodenum through the what?
1. hepatocyte membrane.
2. glucoronic acid, sulphate
2. bile canaliculi
3. sphincter of Oddi
Role of Small Intestine In Bile Metabolism
1. Bile and bile salts increase growth of what?
2. In return, intestinal bacteria metabolise conjugated bile to what?
3. Urobilirubin = _______soluble = what happens because of this?
Fates of reabsorbed Urobilirubin
4. 95% of reabsorbed urobilirubin is what?
5. 5% is what?
6. Small part excreted where?
1. intestinal bacteria
2. urobilirubin (urobilinogen)
3. highly, reabsorbed back into blood
4. excreted again by liver into bile
5. excreted into urine
6. Small part excreted into feces (gives it the characteristic colour)
1. Secreted by cells of the liver into the _________, which drains into the __________.
2. Between meals the duodenal orifice (sphincter of Oddi) is _______and bile flows into the gallbladder, where it is stored (how much?).
3. The bile is concentrated in the_________?
4. Oddi _____within 30 minutes of food intake, the presence of aminoacids and fatty acids in duodenum activates __________, which causes gallbladder contractions and excretion of bile
5, Production……____________ ml of bile daily
1. bile duct, duodenum
2. closed, 50 – 80 ml
4. opens, cholecystokinin
Composition of bile
Remaining smaller components of bile?
1. Water = 97 %
2. Bile salts (0.7%) = primary bile acids are transported to the bile as sodium and potassium salts
1. Bile pigment = glucuronides bilirubin and biliverdin (golden-yellow color of bile)
2. Cholesterol = increased in patients with obstructive jaundice
3. Inorganic salts
4. Fatty acids
5. Lecithin = the main phospholipid of bile
7. Alkaline phosphatase
Two bile salts that make up bile?
1. Cholic acid (converted by colon bacteria to Deoxycholic acid)
2. Chenodeoxycholic acid (converted by colon bacteria to Lithocholic acid)
1. Detectable when the total plasma bilirubin > __mg/dl
2. Causes? 5
-excess production of bilirubin (hemolytic anemia)
-decreased uptake of bilirubin into hepatic cells
-disturbed intracellular protein binding or conjugation
-disturbed secretion of conjugated bilirubin into the bile canaliculi
-intrahepatic or extrahepatic bile duct obstruction
1. Bile is obstructed from flowing where?
2. Occurs if what blocks the duct? 2
3. Conjugated bilirubin builds up in the biliary duct and what increases?
4. How is conjugated bili returned to the blood?
5. So what is a good diagnostic test for obstructive jaundice?
6. What will unconjugated levels of bili be in obstructive?
1. biliary duct
2. gall stones, tumors
3. pressure within the biliary duct increases
-rupture of the bile caniliculi
-via lyphmphatic drainage by the liver
5. conjugated bili
6. normal or low
Formation and secretion of bile
1. Detoxification of various substances - such as? 3
2. Synthesis of plasma proteins - ? 4
3. Coagulation –? 1
4. Blood reservoir – ?1
5. Immunity in the form of what?
6. Vitamins - metabolism and storage of vitamins ? 3
7. Relation to blood formation - ? 3
-Metabolic products of intestinal microbes,
-Exogenous toxins (medicaments, alcohol, poisons),
-Hormones (thyroxine, estrogen, cortisol, aldosterone)
-Steroid-binding and other hormone-binding proteins
3. synthesis of coagulation factors
4. filtration, storage of blood (up to1L)
5. Kupfer cells/macrophages
6. A, D, B12
-storage of vitamin B12,
-metabolism of iron and its storage as ferritin,
-production of erythropoietin
1. Gallbladder attached where?
2. Stores how much bile?
3. Ducts of the gallbladder? 3
1. Attached to surface of the liver
2. Blind pouch that stores bile (50ml)
-Common Bile Duct
Cirrhosis leads to 1._________which can obstruct Blood and Bile flow. Obstruction of hepatic venous blood flow can increase pressures within other veins leading to other circulatory diseases such as what? 2
1. Scar tissue
2. varices & ascites
1. Main duct (Wirsung) runs the entire length of________?
2. Joins CBD at the what?
3. _______mm in diameter, drains up to 20 secondary branches
4. Ductal pressure is ________mm Hg (vs. 7 – 17 in CBD) thus preventing reflux and damage
5. Lesser duct (________) drains superior portion of head and empties separately into 2nd portion of duodenum
2. ampulla of Vater
3. 2 – 4
4. 15 – 30
Innervation of the Pancreas
1. Sympathetic fibers from the ?
2. Parasympathetic fibers from the?
3. Parasympathetic fibers stimulate both ______ and ______secretion
4. Sympathetic fibers have _______effect
5. Rich _______ sensory fiber network
6. What (2) blockade interrupt somatic fibers (pancreatic pain)?
1. splanchnic nerves
3. exocrine and endocrine
6. Ganglionectomy or celiac ganglion
1. Exocrine—Acinar Cells do what?
Endocrine—Islets of Langerhans have four major cell types. What are they?
1. Secretes essential digestive enzymes through pancreatic duct into duodenum
Endocrine—Islets of Langerhans
Four major cell types
1. Alpha (A) cells secrete glucagon
2. Beta (B) cells secrete insulin
3. Delta (D) cells secrete somatostatin
4. F cells secrete pancreatic polypeptide
--These Secretes insulin and glucagon into blood stream
Physiology – Exocrine Pancreas
1. _________ml pancreatic fluid secreted per day
2. Alkaline pH results from what?
3. Centroacinar cells and ductular epithelium secrete what? and how much?
4. Fluid (pH from 7.6 to 9.0) acts as a vehicle to carry inactive proteolytic enzymes to the what?
5. Enzymes digest what? 3
1. 500 to 800
2. secreted bicarbonate which neutralizes gastric acid and regulate the pH of the intestine
3. 20 mmol of bicarbonate per liter in the basal state
4. duodenal lumen
5. carbohydrates, proteins, and fats
1. Major stimulants? 4
2. Major inhibitors? 4
3. Secretin - released from the duodenal mucosa in response to a duodenal luminal pH less than?
1. Major stimulants
2. Major inhibitors
-Pancreatic polypeptide and
1. only digestive enzyme secreted by the pancreas in an ______form?
2. functions optimally at a pH of___?
3. hydrolyzes starch and glycogen to what? 4
4. function optimally at a pH of_____?
5. emulsify and hydrolyze fat in the presence of _______?
4. 7 to 9
5. Bile salts
1. Insulin is synthesized where?
2. ___% of the islet cell mass must be surgically removed before diabetes becomes clinically apparent
1. Synthesized in the B cells of the islets of Langerhans
Regulation of Pancreatic Secretion
1. Acinar cells (enzymatic secretion). _______ is most important stimulant?
1. Secretion of CCK in presence of what (2)in intestinal lumen?
2. Ductal cells (aqueous secretion of ________)
3. Secretin (from __cells of duodenum) is major stimulant
4. Secreted in response to ___in intestine
1. amino acids and fatty acids
1. ___ portions
2. Sphincter of Oddi __cm from pylorus
3. Posterior ulcers _____?
4. Anterior ulcers______?
5. Hugs ______of pancreas
6. _______portion most vulnerable to traumatic rupture
1. Includes what kind of substances? 3
2. Regulate functions of GI tract. Such as? 4
2. Regulate functions of GI tract
-Contraction and relaxation of smooth muscle wall and sphincters
-Secretion of enzymes for digestion
-Secretion of fluid and electrolytes
-Regulate secretion of other GI peptides
Hormones and Paracrines that act in digestion
Digestion via________ must precede absorption
Causes of Malabsorption of Nutrients 2
1. Anything that interferes with delivery of bile or pancreatic juice
2. Damaged intestinal mucosa (e.g., bacterial infection)
Functions of Small intestine
1. Electrolyte Absorption 6
2. Water absorption 3
1. Mostly along the length of small intestine
2. Iron and calcium are absorbed in duodenum
3. Na+ is coupled with absorption of glucose and amino acids
4. Ionic iron is stored in mucosal cells with ferritin
5. K+ diffuses in response to osmotic gradients
6. Ca2+ absorption is regulated by vitamin D and parathyroid hormone (PTH)
1. 95% is absorbed in the small intestine by osmosis
2. Net osmosis occurs whenever a concentration gradient is established by active transport of solutes
3. Water uptake is coupled with solute uptake
1. Intestinal lining increases what?
2. What are Villi?
3. What are Microvilli? 2
1. absorptive surface area
2. Finger-like projections of the mucosa
-Tiny projections on luminal membrane of each intestinal cell
-Give the apical region striated appearance called brush border
Describe and explain the steps in Carbohydrate Digestion
Describe and explain the steps in Protein Digestion
Describe the digestion of Fat
Describe the digestion of Nucleic Acids
Where does the small intestine empty into the large intestine?
Functions of the large intestine
1. Reabsorb water and compact material into feces
2. Absorb vitamins produced by bacteria
3. Store fecal matter prior to defecation
The physiology of different colon regions
1. The ascending colon is specialized for what?
2. The transverse colon is specialized for what? 2
3. The descending colon is a conduit between the what?
1. processing chyme delivered from the terminal ileum
2. the storage and dehydration of feces and is the primary site for the removal of water and electrolytes and the storage of feces
3. transverse and sigmoid colon
The physiology of the rectosigmoid region, anal canal, and pelvic floor musculature is what?
maintains fecal continence
The sigmoid and rectum are reservoirs with a capacity of up to 500mL
Motility in the Large Intestine
1. The proximal half of the colon is concerned with _________and the distal half with_______?
2. The transit of small labeled markers through the large intestine occurs in ______hrs
Movements of the colon
2. Mixing movements?
4. Propulsive movements?
1. absorption, storage
4. (Mass Movements)
Mixing movements (Haustrations)
1. Ring-like contractions (about 2.5 cm) of the circular muscle divide the colon into pockets called______?
2. Net forward propulsion occurs when what?
2. sequential migration of haustra occurs along the length of the bowel
Propulsive movements (Mass Movements)
1. The motor events in the ________ and ___________colon?
2. May be triggered by the increased delivery of _____ ______into ascending colon following a meal (_______ reflex)
3. Irritants, e.g., castor oil, threatening agents such as parasites and enterotoxins can initiate what?
4. Starts in the ______of transverse colon and is preceded by ________ of the circular muscle and the downstream disappearance of haustral contractions
1. transverse and descending
2. ileal chyme, gastrocolic
3. mass movement
4. middle, relaxation
Reabsorption in the large intestine includes: 5
2. Vitamins – K, biotin, and B5
3. Organic wastes – urobilinogens and sterobilinogens
4. Bile salts
1. Villi in the large instestine?
2. Mucosa contains numerous tubular glands called______?
3. Responsible for what?
3. mucus secretion
1. Terminates where?
2. How long?
3. Used for?
1. Terminates at the anal canal
2. 15 cm
What does feces contain?
2. dietary fiber,
3. inorganic salts,
4. dead cells,
5. bacteria, and
6. anything the body cannot or will not absorb.
Water‑ all but about 100 ‑200ml reabsorbed, about 500ml residue enters LI/day, thus about _____ml vol leaves as feces
Sensory innervation and continence
1. What in the rectum detect distention and supply the ENS?
2. The anal canal in the region of the skin is innervated by what nerves that transmit signals to CNS?
3. This region has sensory receptors of what? 3
4. Contraction of what (2) blocks the passage of feces and maintains continence?
3. pain, temperature and touch
4. internal anal sphincter and puborectalis muscle
1. Rectum fills with feces increasing what?
2. Contractions of what (2) create intra-abdominal pressure which increases intra-rectal pressure?
3. ________ relaxes
4. Feces to enter the______?
5. _________waves push the feces out of the rectum.
6. Relaxation of the what (2) allows the feces to exit from the anus?
7. What pull the anus up over the exiting feces (physiologic valve)?
2. abdominal and pelvic floor muscles
6. internal and external anal sphincters
7. Levatori ani muscles