Chapter 23

What is an accessory organ, name the accessory organs of the digestive system.

And accessory organ assist in digestion, secreting chemicals or mechanically breaking down particles. Accessory organs are the teeth, tongue, gallbladder, salivary gland's, liver, and pancreas.

Compare and contrast the short and long reflexes, what are the roles of the sympathetic and parasympathetic nervous system?

Short reflexes are controlled by enteric nervous plexus (gut brain) and respond to stimuli in the G.I. tract. Long reflexes respond to stimuli inside or outside of the gut from the autonomic nervous system. The Parasympathetic System enhances digestive process, while the Sympathetic System inhibits digestion.

Discuss the formation of HCl in parietal cells.

Parietal cells pump H+ until stomach lumen through H+/K+ ATPase. As H+ is pumped into stomach lumen HCO3- is exported back in blood through Cl- and HCO3- antiporter. This results to an increase of HCO3- in blood leaving the stomach, this is referred to as alkaline tide. Cl- is pumped out to lumen to join with H+ forming HCl.

What is the importance of the rectal valves?

three rectal valves stop feces from being passed with gas

Describe the composition of bile.

- a yellow/green alkaline solution containing bile salts/ bilirubin pigments, cholesterol, triglycerides, phospholipids, and electrolytes formed by hepatocytes

How big is the stomach? What allows the stomach to expand so much?

An empty stomach is about 50 ML and can expand to 4 L when full. Rugae.

List and describe the subdivisions of the large intestine, including subdivisions of the colon.

-Cecum: first part of large intestine -Appendix: masses of lymphoid tissue ~Part of MALT of immune system ~Bacterial storehouse capable of recolonizing gut when necessary ~Twisted shape of appendix makes it susceptible to blockages -Colon: has several regions, most which are retroperitoneal (except for transverse and sigmoid regions) -Ascending colon: travels up right side of abdominal cavity to level of right kidney ~Ends in right-angle turn called right colic (hepatic) flexure -Transverse colon: travels across abdominal cavity -Ends in another right-angle turn, left colic (splenic) flexureDescending colon: travels down left side of abdominal cavity -Sigmoid colon: S-shaped portion that travels through pelvis -Rectum: three rectal valves stop feces from being passed with gas (flatus) -Anal canal: last segment of large intestine that opens to body exterior at anus Has two sphincters Internal anal sphincter smooth muscle External anal sphincter skeletal muscle

Discuss the need for regulation of chyme entering the small intestine.

-Chyme entering duodenum is usually hypertonic has to be slow to prevent osmotic loss of water from blood -Low pH of chyme has to be adjusted upward -Chyme has to be mixed with bile and pancreatic juice to continue digestion -Enterogastric reflex and enterogastrones control movement of food into duodenum to prevent it from being overwhelmed

Discuss the modification of the small intestines that make it more efficient in absorption.

-Modified to have huge surface area for absorption Increased 600× to ~200 m2 (size of a tennis court). Circular folds: -Permanent folds ~1 cm deep that force chyme to slowly spiral through lumen -allows more time for nutrient absorption Villi: -Fingerlike projections of mucosa ~1 mm high -contain lacteals -capillariy bed and lymphatic capillaries for absorption Microvilli: -Brush border Cytoplasmic extensions of mucosal cell -Brush border enzymes membrane-bound enzymes carbohydrate and protein digestion

What is the saliva composed of?

-Mostly Water (97-99.5%) -Slightly Acidic (pH of 6.75 to 7.00) -Electrolytes -Digestive Enzymes: Salivary Amylase and Lingual Lipase - Proteins: Mucin, Lysozyme and IgA - Metabolic Wastes: Urea and Uric Acid

Describe the four tunics of the esophagus.

-The mucosa is stratified squamous epithelium and changes to simple columnar at stomach. -The submucosa has an esophageal gland that secretes mucus to aid and bolus movement. - The muscularis externa is the skeletal muscle at the beginning and the Mixtown skeletal and smooth muscle is in the middle. The smooth muscle at the end. - Serosa is replaced by adventitia

Describe the Mucosa of the large intestine, how is it different than the small intestine?

-Thicker than other areas -Simple columnar epithelium ,Except in anal canal -Stratified squamous epithelium to withstand abrasion -No circular folds, villi, or digestive secretions -Lots of deep crypts goblet cells

List and describe the six steps in breaking down food

1) Ingestion is eating; 2)Propulsion is the movement of food through the alimentary canal which includes swallowing and peristalsis which is the major means of propulsion of food that involves alternating waves of contraction and relaxation. 3) Mechanical breakdown includes chewing, mixing food with saliva, turning food in the stomach and segmentation (constriction of intestine that makes food with digestive juices) 4) Digestion is a series of catabolic steps that involves and same to break down complex food molecules into chemical building blocks 5) Absorption is the passage of digested fragments from lumen of the G.I. tract into blood or lymph. 6) Defecation is the elimination of indigestible substances through the anus and form of feces

Describe the anal canal.

Anal columns: -long ridges or folds Anal recesses: -between anal columns -secrete mucus to aid in emptying Pectinate line: -horizontal line that parallels anal sinuses -Visceral sensory nerves innervate area superior to this line -Region insensitive to pain -Somatic nerves innervate inferior to this line -Region sensitive to pain

Describe the three phases of gastric secretion.

1.) Cephalic (reflex) phase is a conditioned reflex triggered by aroma, taste, site, and thought. It varies based on life experience. 2.) The gastric phase (Stimulation) lasts 3-4 hours. This phase releases 2/3 of the gastric juice. Stimulation of gastric phase is distention (stretching) activate stretch receptors which initiates both long and short reflexes. And chemical stimuli stimulates the gastric phase. 2.) The gastric phase (Inhibition) has low pH which inhibits gastric secretion and happens between meals. And also occurs during digestion as negative feedback mechanism. The more protein the more HCl acid is secreted. 3.) The intestinal phase (stimulation) is brief stimulation followed by inhibition. It is partially digested food into small intestine causing a brief Elise of intestinal gastrin. 3.) Intestinal phase (inhibition) ; four main factors in duo denum cause inhibition of gastric secretions: - distention of duodenum due to entry of chyme - presence of acidic chyme - presence of fatty chyme - presence of hypertonic chyme 2 mechanisms: enterogastric reflex and enterogastrons

Describe pancreatic juice, what enzymes does it contain and what do they do?

1200-1500 ml a day. It is a watery, alkaline solution with a pH of 8. It neutralizes acidic chyme. It has electrolytes mostly HCO3-. It also has digestive enzymes such as proteases, amylase, lipases, and nucleases.

Describe motility in the small intestine after a meal, and between meals.

After a meal: Segmentation is most common motion of small intestine -Initiated by intrinsic pacemaker cells -Mixes/moves contents toward ileocecal valve -Intensity is altered by long and short reflexes and hormones -Parasympathetic increases motility; sympathetic decreases it Between meals: -Peristalsis increases -initiated by rise in hormone motilin in late intestinal phase (every 90-120 minutes) -Meal remnants, bacteria, and debris are moved toward large intestine -Complete trip from duodenum to ileum takes ~2 hours

How much chyme is put into a duodenum at a time? What happens to the other 27 ML?

About 3 ml spurts into the duodenum. The rest of the 27 ml force backward into the stomach.

What is appendicitis and why is it dangerous?

Acute inflammation of appendix. Venous drainage can be impaired. Ruptured appendix can cause peritonitis.

Describe the blood and nerve supply to the small intestine.

Blood supply: -The Superior mesenteric artery brings blood supply -Veins (carrying nutrient-rich blood) drain into superior mesenteric veins, then into hepatic portal vein, and finally into liver Nerve supply: -Parasympathetic innervation vagus nerve -Sympathetic innervation thoracic splanchnic nerves

List and describe the subdivisions of the small intestine.

Duodenum: mostly retroperitoneal ~25.0 cm (10.0 in) long curves around head of pancreas has most features Jejunum: ~2.5 m (8 ft) long attached posteriorly by mesentery Ileum: ~3.6 m (12 ft) long attached posteriorly by mesentery joins large intestine at ileocecal valve

Describe general tooth structure. Be able to label the parts on a diagram.

Each tooth has two major regions the crown and root. The crown is the exposed part above gingiva (gum). It is covered by enamel, the hardest substance in the body. The root is the portion embedded in the jawbone and it is connected to the crown by the neck.

What are the effectors in the digestive reflexes and what do they do?

Effectors of digestive activity are smooth muscle and glands. Receptors initiate. The stimulation of smooth muscle mixes and move contents. Activation or inhibition of digestive glands secrete digestive juices or hormones.

Enzymes are secreted in an inactive form and activated in the duodenum, why and how?

Enzymes are secreted in the inactive form to regulate the proper function of the enzyme. It is released in an inactive form first and goes to the target organ and then is activated when it is needed. In the case of the pancreas, it secretes zymogens partly to prevent the enzymes from digesting proteins.

Where do the digestive enzymes and bile used in the small intestine come from?

Enzymes for digestion come from: -Liver and pancreas bile, bicarbonate, digestive enzymes not brush border enzymes -Brush border enzymes bound to plasma membrane Responsible for final digestion of chyme

What causes vomiting?

Extreme stretching and intestinal irritants such as bacterial toxins, excessive alcohol, spicy food and certain drugs cause vomiting.

Describe the intestinal crypts, list the cell types and functions of the cells.

Five main types of cells found in villi and crypts -Enterocytes Most of the epithelial cells Simple columnar absorptive cells bound by tight junctions and contain many microvilli Function Villi: absorb nutrients and electrolytes Crypts: produce intestinal juice, watery mixture of mucus that acts as carrier fluid for chyme -Goblet cells mucus-secreting cells found in epithelia of villi and crypts -Enteroendocrine cells Produce enterogastrones examples: CCK and secretin Found scattered in villi but some in crypts -Paneth cells Deep in crypts Secrete antimicrobial agents defensins and lysozyme -Stem cells Continuously divide Produce other cell types Villus epithelium renewed every 2-4 days

What are the functions of the oropharynx and laryngopharynx?

Food passes from the mouth into the oropharynx and then into the laryngopharynx. It allows passage of food, fluids and air.

What is the function of the ileocecal valve and how is it regulated?

Ileocecal sphincter relaxes and admits chyme into large intestine when: -Gastroileal reflex enhances force of segmentation in ileum -Gastrin increases motility of ileum -Ileocecal valve flaps close when chyme exerts backward pressure -Prevents regurgitation into ileum

Describe incisors, canines, premolars, and molars and relate their structure to their functions.

Incisors: chisel shaped for cutting Canines: fang like teeth that tear or pierce Premolars: broad crowns with rounded cusps used to grind or crush Molars: broad crowns, rounded cusps, best grinders. During chewing, upper and lower molars locked together creating tremendous crushing force.

Identify were each of the following happens: ingestion, mechanical digestion, chemical digestion, propulsion, absorption

Ingestion happens in the mouth. Mechanical digestion happens in the mouth, stomach, and the small intestine. Chemical digestion happens in the stomach. Propulsion happens in the oral pharynx, esophagus, stomach, small and large intestine. Absorption happens in the lymph and blood vessels. Defecation happens in the anus.

Compare and contrast intraperitoneal and retroperitoneal; Which organs are retroperitoneal and which are intraperitoneal?

Intraperitoneal organs are located within the Peritoneum while retroperitoneal organs are located outside or posterior to the peritoneum. Intraperitoneal: Stomach,half of the First part of the duodenum, jejunum, ileum, cecum, appendix, transverse colon, sigmoid colon, rectum Retroperitoneal: The rest of the duodenum, ascending colon, descending colon, rectum

Describe extrinsic control of the digestive system

Involve long reflexes (autonomic nervous system)

Describe the modifications of the muscularis externa and mucosa that allow the stomach to perform its specialized functions.

It has a regular Circular and longitudinal smooth muscle layers an extra third layer, the oblique layer. It allows the stomach to turn, mix, and move chyme. Also allows pummeling motion which increases physical breakdown and forces chyme into small intestine. The mucosa secrete to layer coats of alkaline mucus and the surface layer traps bicarbonate rich fluid layer beneath it. Gastric pits lead into gastric glands and gastric glands make gastric juice.

Describe the composition of the submucosa of the G.I. tract

It has areolar connective tissue. The blood and the lymphatic vessels, lymphoid follicles, and submucosal nerve plexus that supply surrounding the G.I. tract tissues. It has lots of elastic tissues which help organs to regain shape after storing large meals.

Describe the general structure of the muscularis externa and its function

It is a muscle layer that is responsible for segmentation and peristalsis. It is an inner circular muscle layer and circular layer thickens in some areas to form sphincters. Outer longitudinal layer.

Describe the structure and function of the esophagus.

It is a muscular tube that runs from the laryngopharynx to the stomach and it is collapsed when not involved in food propulsion. It goes to the diaphragm at esophageal hiatus. It also joins the stomach at cardial orifice.

Why is decay a problem in baby teeth?

It is a problem and baby teeth because it can be painful and lead to serious infections. It can cause damage to the permanent teeth and primary teeth deserve as much attention as permanent teeth. The baby teeth or primary teeth service important place holders for the developing permanent teeth yet to come.

What is the dental formula?

It is a short hand indicator of number and position of teeth. Shows ratio of upper to lower teeth for only half of mouth, other side is a mirror image.

Describe the epithelium of the mucosa, what are its functions, how does it change and move down the G.I. tract?

It is a simple columnar epithelium and mucus secreting cells and most of the tract. The mouth, esophagus, and anus are made up of stratified squamous epithelium. It secretes mucus which protects the organs from enzymes and eases food passage. It also makes a crate enzymes and hormones in the stomach and small intestine.

Describe the gallbladder and give its functions.

It is a thin walled muscular sac on the ventral surface of the liver. It's function is to store and concentrate bile by absorbing water and ions.

Describe the path bile follows beginning with formation and going to the small intestine.

It is collected by a system of ducts that flow from the liver through the right and left hepatic ducts. These ducts ultimately drain into the common hepatic duct. The common hepatic duct then joins with the cystic duct from the gallbladder to form the common bile duct.

Describe the control of gastric secretion.

It is controlled by neural mechanisms and hormonal mechanisms. In neural mechanisms the parasympathetic (Vagus Nerve) stimulation increases secretion, and the sympathetic stimulation decreases secretion. And hormonal mechanisms gastrin stimulates hydrochloric acid secretion by the stomach and stimulates gastrin antagonist hormones by the small intestine.

What is xerostomia and what causes it?

It is dry mouth and two little saliva is being made. Medications, diabetes, HIV or AIDS, and Sjogren's Syndrome can cause it.

Describe the lamina propria, what are its functions?

It is made up of loose areolar connective tissue and a rich supply of capillaries located here. It also contains lymphoid follicles that help defend against micro organisms.

Describe the regulation of gastric emptying?

It is regulated by the duodenum. It controls how much chyme enters, prevents overfilling, and duodenal receptors respond to stretch and chemical signals, enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal filling.

Describe the gross anatomy of the liver.

It is the largest gland in the body and weighs about 3 pounds. It consists of four primary lobes: right, left, caudate, and quadrate. The falciform ligament separates larger right and smaller left lobe's and suspends the liver from the diaphragm and anterior abdominal wall. The round ligament is the remnant of fetal umbilical vein along free edge of falciform ligament.

What are the functions of the stomach?

It is the temporary storage tank that starts chemical breakdown of proteins, converts bolus of food to paste like chyme, end it is extremely expandable. When empty, stomach mucosa forms many folds called rugae.

Discuss the exocrine functions of the pancreas.

It produces pancreatic juice. Acini are clusters of secretory cells and they produce zymogen granules with proenzymes. The ducts secrete to the duodenum through main pancreatic duct and the smaller duct cells produce water and bicarbonate.

What happens when the stomach fills?

It stretches to accommodate incoming food.

Describe the pancreas.

It's mostly retroperitoneal, deep to greater curvature of the stomach, the head is encircled by the duodenum, and the tail ends at the spleen.

Describe the small intestine.

Major organ of digestion and absorption (where most of it happens). 2-4 m long.

What stimuli trigger digestive activity?

Mechanical and chemical stimuli trigger digestive activity. Receptors are located in walls of G.I. tract organs. Stretch, changes in osmolarity and pH, and presence of substrate and end products of digestion. Parasympathetic system triggers digestive activity overall.

How is salivation controlled?

Minor glands continuously keep the mouth moist. Major salivary gland's activated by parasympathetic nervous system when: - ingested food stimulates chemo receptors and mechanoreceptors in mouth - strong sympathetic stimulation in Hibbett salvation and results and dry mouth *Smell and sight of food or upset GI can act as stimuli

How much gastric juice is secreted per day?

More than 3 L of gastric juice is secreted per day.

List in order the organs of the digestive system.

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, and the anus.

Beginning at the lumen and going out where it list the four tunics of the G.I. tract

Mucosa, submucosa, muscularis externa, and serosa

What is MALT? Describe the MALT structures of the small intestine.

Mucosa-associated lymphoid tissue (MALT) -protects intestine against microorganisms -Individual lymphoid follicles

Describe intrinsic control of the digestive system

Neurons and hormones control digestive activity and these controls are known as intrinsic and extrinsic controls. Intrinsic controls involve short reflexes (enteric nervous system)

What is the role of pepsin in protein digestion? HCl acid?

Pepsin is an enzyme that digest proteins. HCl acid denatures proteins.

What activates the pepsinogen secreted by the chief cells and where is it produced?

Pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with hydrochloric acid produced by gastric parietal cells. It is produced in the stomach.

Describe peristalis and compare it to the segmentation.

Peristalsis is an adjacent segment of the alimentary canal organs alternately contracting and relaxing. Food is moved distally along the tract and it is primarily propulsive; some mixing may occur. Segmentation is a non-adjacent segment of the elementary canal organs contracting and relaxing and food is move forward then backward. Primarily mix his food and breaks it down mechanically some propulsion may occur.

What is peritonitis, what causes it, what are the dangers and what is done to treat it?

Peritonitis is inflammation of the peritoneum. It can be caused by piercing the abdominal wound, ulcers, or ruptured appendix. It is dangerous and lethal if it becomes widespread (sepsis). For treatment : Debris removal and mega doses of antibiotics

When do the primary teeth normally erupt? Permanent teeth?

Primary teeth erupt between six and 24 months of age while permanent teeth erupt around 6 to 12 years of age.

How is serosa different in peritoneal versus retro peritoneal organs

Retroperitoneal organs have both an adventitia and a serosa.

Which parts of the large intestines are retroperitoneal, and intraperitoneal?

Retroperitoneal: Cecum, appendix, and rectum Colon (except transverse and sigmoid) Intraperitoneal regions: anchored to posterior abdominal wall by mesentery sheets called mesocolons

What are the functions of the tongue?

The tongue occupies the floor of the mouth. The functions include: -Gripping, repositioning, and mixing of food during chewing -Formation of bolus, mixture of food and saliva -Initiation of swallowing, speech and taste

Describe the muscularis mucosae and give its function

Smooth muscle that produces local movements of mucosa

Describe circulation in the digestive system. What is splenic circulation? What is hepatic portal circulation?

Splanchnic Circulation: arteries branch off of the aorta, serves digestive organs. -Hepatic, splenic, and left gastric arteries -inferior and superior mesenteric arteries Hepatic Portal Circulation: drains blood from digestive organs, blood goes directly to the liver for processing

Compare and contrast nervous and hormonal controls of the digestive tract.

The Nervous Controls are intrinsic and extrinsic. Neurons and hormones control digestive activity. Hormone controls our hormones from the stomach and small intestine they stimulate target cells to secrete or contract. Target cells can be in the same or in different organs.

Describe the layers of the peritoneum and explain its function

The Peritoneum are serious membranes of abdominal cavity that consist of the Visceral Peritoneum and the Parietal Peritoneum. The visceral peritoneum is the membrane on the external surface of most digestive organs. The perinatal peritoneum is the membrane that lines the body wall. The peritoneal cavity is a fluid filled space between two Peritoneums and the fluid lubricates mobile organs.

Describe the two phases of degltuition (swallowing).

The buccal phase is the voluntary contraction of the tongue. The pharyngeal esophageal phase primarily involves the vagus nerve and it is controlled by swallowing center in the medulla and lower pons.

Describe the major regions of the stomach.

The cardial part surrounds cardial orifice. The fundus is a dome shaped region beneath the diaphragm. The body is the midportion. The pyloric part is wider and more superior portion of pyloric region, antrum, narrows into pyloric canal that terminates into pylorus. The pylorus is continuous with the duodenum through the pyloric valve.

Compare the dentition seen in primary teeth to the dentition seen in permanent teeth.

The dentition in primary teeth are 20 deciduous teeth, or milk baby teeth. They erupt between six and 24 months of age. The dentition in permanent teeth are 32 deep lying enlarged and develop teeth. The roots of baby teeth are reserved from below they loosen and fall out. Occurs around 6 to 12 years of age and all are in by the end of adolescence.

Describe the alimentary canal.

The elementary canal is a continuous muscular tube that opens to the outside at both ends, digest food, and absorbs nutrients.

Describe the histology of the liver. What is the functional unit?

The functional unit of the liver are the lobules.

Describe the curvature of the stomach, where are each of the mesentery attached and what do they connect?

The greater curvature is the complex lateral surface of the stomach. The lesser curvature is the concave medial surface of the stomach. Mesenteries extend from curvature's and hold the stomach to other digestive organs.

Describe the circulation of the liver.

The hepatic artery and vein enter the liver at Porter Hepatis. The bile ducts are: Common Hepatic Duct: leaves the liver Cystic Duct: connects to gallbladder Bile Duct: Union of common hepatic and cystic ducts

What are the digestive functions of the liver, gallbladder and pancreas?

The liver makes bile, and bile emulsifies fat. The gallbladder stores bile. The pancreas produces several digestive enzymes and produces bicarbonate to neutralize stomach acid.

List the major salivary gland and describe the locations

The major salivary gland's are: outside of the oral cavity and produce most of the saliva. Parotid: anterior to the ear and external to the masseter muscle. Parotid duct opens into oral vestibule next to second upper molar. Submandibular: it is medial to the body of the mandible and the duct opens at base of lingual frenulum Sublingual: it is anterior to the submandibular gland under the tongue and it has 10 to 12 ducts into the floor of the mouth

What is mesentery and what is its function?

The mesentery is a double layer of peritoneum that extends from body wall to digestive organs. It provides routes for blood vessels, lymphatics, and nerves. It also holds organs in place and stores fat.

Describe the structure of the mouth

The mouth is also known as the oral buccal cavity. It is bounded by lips anteriorly, cheeks laterally, palate superiorly, and tongue inferiorly. The oral orifice is the anterior opening. Walls of the mouth lined with stratified squamous epithelium and these cells are tough and resist abrasion. Cells of gums, hard palate, and part of tongue are keratinized for extra protection.

Describe the Mucosa, what are its functions, what are it's layers?

The mucosa lines the lumen. The different layers perform one or all three functions. Secretion: mucus, digestive enzymes, and hormones Absorption: end products of digestion Protection: against infectious disease It is made up of three sublayers: Epithelium, Lamina Propria, Muscularis Mucosae

Describe the mucosal barrier of the stomach, what is its function?

The mucosal barrier protects the stomach and it is a thick layer of bicarbonate rich mucus that has tight junctions between epithelial cells which prevent juice seeping underneath tissue. Damaged epithelial cells are quickly replaced (surface cells replaced every 3-6 days)

Describe the four types of glands found in the stomach mucosa, what does each produce?

The mucous neck cells secrete thin, acidic mucus of unknown function. The parietal cells secrete hydrochloric acid and intrinsic factor. Chief cells secrete pepsinogen and lipases. Pepsinogen is an active enzyme that is activated to pepsin by HCl and by pepsin itself. Enteroendocrine cells secrete chemical messengers into lamina propria and act as paracrines (serotonin and histamine). Also hormones such as somatostatin and gastrin enteroendocrine cells.

Describe the structure of the palate

The pallet forms the roof of the mouth and has two distinct parts. The hard palate is formed by palatine bones and palatine processes of maxillae with a midline ridge called raphe. The mucosa slightly corrugated to help create friction against tongue. The soft palate is a fold formed mostly of skeletal muscle and it closes off the nasopharynx during swallowing. The uvula are fingerlike projections that face down word from free edge of soft palate.

Describe the structure and function of the pharynx.

The pharynx allows food, fluids and air to pass through. It has stratified squamous epithelium lining with mucus producing glands and the external muscle layers consist of two skeletal muscle layers. The inner layer of muscles runs longitudinally. The outer pharyngeal constrictors encircle the wall of the pharynx.

How long does it take to empty the stomach?

The stomach empties in about 4 hours.

Describe the papillae of the tongue, which have tastebuds?

The superior surface bears papillae, peg like projections of underlying mucosa. Filiform Papillae: gives tongue roughness to provide friction; only one that DOES NOT contain taste buds; gives tongue a whitish appearance Fungiform Papillae: mushroom shaped, scattered widely over tongue; vascular core causes reddish appearance of tongue. Vallate (Circumvallate) Papillae: 8 to 12 form V shape; row in back of tongue. Folliate Papillae: located on lateral aspects of posterior tongue

Describe the structure of the tongue.

The tongue is composed of interlacing bundles of skeletal muscle. Intrinsic muscles change the shape of the tongue an extrinsic muscles alter the tongues position. The lingual frenulum is the attachment to the floor of the mouth.

Identify the two types of secretary cells found in the salivary gland and what each produces.

The two types of secretory cells are serous cells and mucous cells. Serous cells secretion is mostly water, plus enzymes, ions, and bit of mucin. Mucous cells produce mucus. The parotid and submandibular gland contain mostly serous cells, while the sublingual gland consists mostly of mucous cells.

95% of bile salts are recycled, explain how.

They are recycled through enterohepatic circlation. The bile salts are reabsorbed into the blood by the ileum, return to the liver through hepatic portal blood, and re-secreted in newly formed bile.

How are secretions from the pancreas and secretions of bile regulated?

They are regulated by neural and hormonal controls. Hormonal controls include CCK and secretin. Bile secretion is increased when: -Enterohepatic circulation returns large amounts of bile salts. - Secretin, from intestinal cells exposed to HCl and fatty chyme, stimulates gallbladder to release bile - Hepatopancreatic sphincter is closed, unless digestion is active Bile is stored in gallbladder and released to small intestine only with contraction.

What are the functions of hepatocytes?

They produce about 900 ML of bile per day. They process blood-borne nutrients, store fat soluble vitamins, and perform detoxification (converting ammonia to urea)

Describe the large intestine. What are the specialized structures?

Three unique features: 1.)Teniae coli: three bands of longitudinal smooth muscle in muscularis 2.)Haustra: pocketlike sacs caused by tone of teniae coli 3.)Epiploic appendages: fat-filled pouches of visceral peritoneum

What are the functions of saliva?

To clean the mouth, dissolve chemicals for taste, moisten food; compacts into blous, begins breakdown of starch with enzyme amylase

What is the only essential function of the stomach? What is this for?

To digest proteins. Protease enzymes break down proteins into amino acids. Digestion of proteins in the stomach is helped by stomach acid, which is strong hydrochloric acid. This kills harmful microorganisms that may be in the food.

What are the functions of the digestive system?

To take in food, break it down into nutrient molecules, absorb molecules into the bloodstream, and red body of any indigestible remains.

What are the health risks associated with tooth and gum disease? What causes these risks?

Tooth and gum disease can increase heart disease and strokes in two ways. The risk factors are smoking, diabetes mellitus, oral piercings and poor oral hygiene.

How much saliva do we produce in a day?

We produce 1500 ml/day