Larynx To Food Entry O Lined W example essay topic

THE DIGESTIVE SYSTEM Divided into two parts: . Alimentary tract o Or Gastrointestinal tract o Hollow tube from mouth to anu so Food material inside the tract is considered to be outside the body b / c the canal is open to the external environment at both end so It digests food and absorbs the digested fragment so Organs include MouthS S Pharynx SS Esophagus SS StomachS S Small intestine Large intestine. Accessory digestive organ so Organs include Teeth SS TongueS S Gall bladder Salivary glands LiverS S Pancreaso The teeth and tongue are in the oral cavity while digestive glands and gallbladder lie outside the GI tract and connect to it by duct so Most of the accessory digestive organs are in the ab domino-pelvic cavity Covered by a serous membrane called the visceral peritoneum Parietal peritoneum covering the abdominal walls of the ab domino-pelvic cavity B / w these two layers is a thin layer of fluid produced by the serous membranes. Lubricates b / c these organs are moving Organs are held in place, and anchored to the abdominal wall (b / c they are moving) by mesentery. A double layer of peritoneum o Sheet of two serous membranes fused back to back that extends to the digestive organs from the body wall.

Also a fat storage area. Provide routes for blood vessels, lymphatics and nerves to reach the digestive viscera GI tract. Hollow tube w/ 4 distinct layer so Central is the hollow portion called the lumen o MucosaS S Layer closest to the lumen Wet epithelial membrane (simple columnar epithelium) SS Often w / a lot of goblet cells to secret mucous. Mucous lubricates food to help it pass through the canal. Mucous lining protects the wall of the GI tract from digestive enzymes (in the stomach and small intestine) and HCl from the stomach-PROTECTIVESS Epithelial layer rests on a thin layer of loose connective tissue called lamina propria. Has a lot of blood vessels to get broken down nutrients into the blood so they can be distributed to tissues.

Blood vessels also nourish the epithelium Beyond the lamina propria is a thin layer of smooth muscle called the muscularis mucosa e. Contraction of this layer moves the epithelium around so food trapped in the mucosa is dislodged and proceeds through the tract. In the small intestine this layer throws the mucosa into a series of small folds that increases the surface area greatly SubmucosaSS Layer of dense connective tissue just external to the mucosa Contains lots of blood vessels, lymphatic vessels, lymphoid follicles and nerve fibers Has a rich supply of elastic fibers that enables the stomach to regain its normal shape after temporarily storing a large meal The vascular network supplies the surrounding tissues of the GI tract wall Muscularis externa Muscular layer Responsible for segmentation and peristalsis In most of the GI tract it is 2 layers of smooth muscle. Inner circular layer. Outer longitudinal layer. In several places along the tract, the circular layer thickens, forming sphincters that act as valves to prevent the backflow and control food passage from one organ to the nex to Visceral peritoneum or SerosaS S Protective outermost layer Formed by areolar connective tissue covered w / mesothelium (a single layer of squamous epithelial cells) FUNCTIONAL ANATOMY OF THE GI TRACT.

Oral cavity (mouth) o Extends form the lips anteriorly to the Lined w / stratified squamous epithelium ProtectiveSS On gums, hard palate and dorsum of the tongue the epithelium is keratinize d to give extra protection against abrasion when eating Lips and cheeks Lips extend from the bottom of the nose to indentation on the chin What we call lips (where lipstick is applied) is called the red margin. This area is red b / c it is poorly keratinize d. No sweat glands, no sebaceous gland so Causes dryness and cracking due to the elements Lips and cheeks help to keep food b / w the teeth when we chew and play a small role in speech. Lips formed by the oris muscle. Cheeks are formed largely by the buccinator so The palate Hard anteriorly. Is the rigid surface that the tongue forces food against when chewing Soft posteriorly.

Mobile fold formed mostly of skeletal muscle. Uvula projects downward from ito Uvula and soft palate rise to close off the nasopharynx when we swallow o The tongue Occupies the floor of the mouth and fills most of the oral cavity when the mouth is closed Skeletal muscle covered w / epithelium During chewing, it grips food and constantly repositions it b / w the teeth Also mixes the food w / saliva forming a compact mass called the bolus and pushes it back into the oro pharynx. Before the oro pharynx, usage of the tongue is voluntary. After the oro pharynx, movement is involuntary and controlled by the medulla and pons Has both intrinsic and extrinsic skeletal muscle fibers. Intrinsic Confined in the tongue and not attached to bone Muscle fibers running in several planes allow the tongue to change shape (but not position) as necessary for speech and swallowing.

Extrinsic o Extend the tongue from their points of origin on the bones of the skull or the soft palate o Protrude, retract and move the tongue from side to side Lingual frenulum is a fold of mucosa that secures the tongue to the floor of the mouth so that it cannot be swallowed Papillae are rough peg-like projections of the tongue. Filiform o Conical in shape Give the tongue surface its rough texture that aids in licking and provides friction for manipulating food. Fungiform Mushroom-shape do Scattered widely on the tongue surface Each has a vascular core, giving them a reddish tin to Some are on the esophagus. Circumvallate o 10-12 arranged in a V, located at the back of the tongue Resemble fungiform but have a surrounding groove. Taste buds are located on the fungiform and circumvallate papillae o Pick up tastes that are sweet, salty, sour and bitter Japanese suggest another taste bud, the um ami, which means delicious Makes you crave protein in red meat Beyond the circumvallate is the sulcus terminal is, a groove that distinguishes the anterior two thirds of the tongue in the oral cavity from the posterior 1/3 in the Salivary glands Extrinsic salivary glands produce most of the saliva. Parotid gland so 2 masses, 1 in front of each ear Secretion is mostly a watery fluid from serous cell so Become inflamed w / mumps.

Submanibular gland so Secretes a watery fluid (serous cells) plus mucous (mucous cells) called Size of a walnut located along the medial aspect of the mandibular body. Sublingual gland so Anterior to the sub mandibular gland under the tongue These are mucous glands Intrinsic salivary glands also called buccal glands are scattered through the oral cavity mucosa Saliva. 97-99.5% water. Mucous. Antibodies. Ions.

Lysozyme, an antibacterial enzyme. Salivary amylase o Begins CHO digestion o Why when you continue to chew bread it begins to taste sweet-b / c you are breaking down the sugars (CHO). Functions Cleanses mouth Dissolves food chemicals so they can be taste do Moistens the food and aids in compacting it into a bolus o Contains enzymes that begin the chemical breakdown of starchy foods Control of salivation. Under control of the parasympathetic nervous system (facial VII, and IX nerves) o Teeth SS 32 permanent teeth Talk of them in quadrants In each jaw (upper and lower) you have. 2 incisors-used for biting. 2 canine-fang like teeth used to tear, piece food (rip apart).

2 pre-molars: grinding or crushing. 3 molars: grinding and crushing o Last of these is the wisdom teeth Tooth structure. Top part, what you see, is the crown. Part you cant see is the root. Gum is called gingiva lo Inflammation of the gum is called gingivitis. Crown of the tooth is covered w / enamel o Hardest substance in the body, containing mostly Cao A cellular material Cells that produce it die, so cannot be replaced.

Root is covered w / a calcified connective tissue called cementum o Cementum connects the tooth to the periodontal ligament which anchors the tooth in an immovable joint (joint). Dentin is a bone like material, underlying the enamel cap forming the bulk of the to otho Produced by odontoblast's. Dentin surrounds the pulp cavity o Contains a number of soft tissue structures (connective tissue, blood vessels and nerve fibers) that are collectively called pulp. The pharynx o From the mouth, food passes posteriorly into the oro pharynx and then the laryngopharynxSS Common passageways for food, fluids and air Stratified squamous epithelium supplied w / mucous producing glands Contractions of the pharyngeal constrictor muscles propel food into the esophagus below. The esophagus o Muscular tube that is collapsed when not involved in food propulsion o After food goes through the it is routed to the esophagus posteriorly as the epiglottis closes off the larynx to food entry o Lined w / stratified squamous epithelium o Slightly thickened portion of the esophageal wall at the junction of the stomach is called the gastro esophageal (cardiac) sphincter SS Supposed to close off the esophagus from the stomach, but does not do that great of a job.

Diaphragm, which surround the sphincter, does a better job of closing off the esophagus. Hiatal hernia, when the stomach protrudes slightly above the diaphragm so diaphragm cannot reinforce the cardiac sphincter o Allows gastric juices to flow into the esophagus particularly when lying down. Stomach Left side of the abdominal cavity and below the esophagus o When empty is collapse so Can stretch to hold up to a gallon of foo do Stomach is not a vital organ to life Only thing of importance is the intrinsic factor which can be artificially injected o Has four regions Cardiac. Small region surrounding the cardiac orifice where food enters the stomach from the esophagus Fundus.

Dome shaped portion tucked beneath the diaphragm. Curves downward Body. Mid portion of the stomach, continuous w / SS Pyloric. Funnel shaped region continuous w / the duodenum. Pyloric sphincter controls passage from stomach to the duodenum of the small intestine; controls stomach emptying o Main purpose of the stomach is to store the food and pass it to the small intestine for digestion o Anchored by 2 membranes (mesenteries) SS Lesser omentum. Runs b / w the liver and the lesser curvature and becomes continuous w / the visceral peritoneum Greater omentum.

From the greater curvature down to cover the small intestine and wrapping the transverse portion of the transcending colon. Riddled w / fat deposits. Passageway for nerves, blood vessels. Large collections of lymph node so Microscopic AnatomySS Lined w / simple columnar epithelium that secretes an alkaline mucous. Inside of stomach is acidic (lots of HCl secreted) so alkaline mucous protects the lining of the stomach, especially the epithelial cells W / in the epithelial lining are holes called gastric pits. Openings leading to gastric glands which produce gastric juices that enter the stomach through the gastric pits.

Gastric juice o Contents vary depending on the region of the stomach In the pyloric and cardiac regions is composed mostly of mucous o Gastric glands of the fundus and body have 4 types of cells (have them everywhere, but highly concentrated in the fundus and body) SS Parietal cells. Release HCl into the stomach. PH in stomach is 1.5-3.5 = VERY ACIDIC. HCl kills bacteria and helps to denature proteins.

ONLY THING DIGESTED IN THE STOMACH IS PROTEIN. Produce intrinsic factor which is needed for B-12 to be absorbed o B-12 needed for healthy RBC Chief cells. Produces pepsinogen, the inactive form of pepsin (protein digesting enzyme) o Activated by contact w / HCl. Pepsin only works well in acidic environment, the stomach. Only protein is digested in the stomach Enteroendocrine cells. Produce hormones concerned only w / digestion.

These hormones get into the blood and only affect the digestive organs. Gastrin-target cell is the parietal cell so If the pH of the stomach rises, become alkaline, gastrin tells the parietal cells to secrete more HCl SS Mucous neck cells. Produce an acidic mucous. Function is unknown The products of all these cells, minus hormones, composes gastric juice Mucosal barrier. Alkaline mucous secreted by epithelial cells that prevents destruction of the stomach by HCl and pepsin. Created by 4 factor so Thick coating of bicarbonate rich mucous o Epithelial cells joined together by tight junctions preventing gastric juice from leaking into the underlying tissue layer so Deep in the gastric glands the external faces of the plasma membrane are impermeable to Hcl Damaged epithelial mucous al cells are shed and replaced quickly by the division of undifferentiated stem cells.

SS Stomach surface epithelium is replaced every 3-6 day so Only digests protein but some things do get into the blood AspirinS S Alcohol When you eat, see or think of food, signal are sent to the brain stimulating the vagus nerve and stimulating glands of the stomach to secrete more gastric juices When food enters the stomach, the expansion of the stomach causes more gastric juices to be released When you start swallowing food and it travels down the esophagus, the parasympathetic nervous system tells muscles to relax and the stomach to expand The ability of the visceral smooth muscle to be stretched w / o increasing its tension or contracting expulsive ly is called plasticity. Allows the stomach to serve as a temporary reservoir for foo do Food enters the stomach and sends waves of contractions called peristaltic waves Start at the cardiac region and continue to the pyloric region producing rippling movements. Become stronger in the pyloric region where the musculature is thicker Happens 3 times a minute Helps to mix the stomach contents w / gastric juices Helps churn material to break it into smaller and smaller pieces In stomach, the muscularis externa has a third layer, an oblique smooth muscle layer. Allows churning of stomach contents Particles need to be broken down small enough to get through the pyloric sphincter. Pyloric sphincter can hold 30 ml of chyme (fluid and small particles produced by churning in the stomach). W / each peristaltic wave, 3 ml or less of chyme spits into the small intestine After a usual meal, the stomach empties in approximately 4 hours.

If the meal is high in fat (digested in the small intestine) it will take longer b / c the small intestine has so much fat to digest, which takes a long time When empty, the stomach collapses into many folds called rug ae. Small intestine o Diameter is one in cho In the living person, it is 8-13 feet long, coiled and folded o It is held in place by the mesentery o AnatomySS Is the tube extending from the pyloric sphincter to the valve Three subdivisions. Duodenum curves around the head of the pancreas and is just beyond the stomach Is about 10 inches long Secretions from the liver (bile) and pancreas (digestive enzymes) enter here through ducts Secretions to the duodenum controlled by the sphincter. Jejunum o About 8 feet long Extends from the duodenum to the ileum. Ileum 12 feet in length Joins the large intestine at the valve o The majority of digestion takes place here CHOSS Proteins Lipids Nucleic acid so Absorption is in the small intestine too Specialized for absorption b / c. Long length increase the surface area over which nutrients are absorbed.

Folds plicae circulates in the mucosa and sub mucosa force chyme to spiral through the lumen o This slows the movement allowing time for absorption. Villi are everywhere on the surface of the small intestine o Finger like projections that are more than a mm high Epithelial cells of the villi are columnar cells, highly absorptive cell so Increases the surface area increasing absorption o Lacteal at the core of each villus Lymph capillary that picks up digested lipid so Core also has a dense capillary bed to pick up absorbed material Lots of goblet cells to secrete mucous. Microvillio Tiny projections on the plasma membrane of absorptive cells (columnar epithelium) only seen w / electron microscope o Function to increase surface are ao Give the mucosa a fuzzy appearance called the brush border Plasma membranes of micro villi contain enzymes referred to as brush border enzymes. Complete the digestion of CHO and protein so Lined w / simple columnar epithelium Lots of goblet cells producing mucous to help food slide through Lining has pits that lead into intestinal crypts or crypts of LieberduhnSS Decrease in number along the length of the intestine Epithelial cells that line the crypts secrete intestinal juice. Watery mixture containing an alkaline mucous Crypts secrete lysozyme an antibacterial enzyme Epithelial cells arise from rapidly dividing stem cells located at the base of the crypts. Every 3-6 days the epithelial lining is replaced.

Treatments for cancer (chemotherapy and radiation) target rapidly dividing cell so Kills cancer cells but also nearly obliterates the GI tract epithelium causing nausea, vomiting and diarrhea after treatment A lot of lymph nodules in the small intestine b / c there is lots of bacteria They increase in size from the duodenum to the ileum In the ileum they are called Peyer's patches. White patches o In the duodenum there are glands called duodenal (Brunner's) glands Make an alkaline mucous that protects the small intestine from the highly acidic chyme from the stomach Also raises the interior of the small intestine to the alkaline range needed for optimal enzymatic action (pH above 7 is necessary) SS When the secretion of alkaline mucous is insufficient, get duodenal ulcers. The Liver Organ that is essential for life-no machine can replace ito Large organ o Three pounds in the adult Located just below the diaphragm, mostly to the righto Has four lobe so Functions Removes nutrients from the blood and stores them Produces bile needed for fat breakdown o Microscopic anatomy The liver is composed of sesame seed-sized structural and functional units called liver lobules. Each lobule is roughly hexagonal (six sided) consisting of liver cells called hepatocytes that are arranged in plates. These hepatocyte plates radiate out form a Central vein like the spokes on a bicycle wheel. In a rough model, open a paperback book so that the covers touch The pages represent the plates of hepatocyte so The hollow cylinder made by the rolled spine is the central vein.

Each liver lobule is surrounded by connective tissue that has blood vessels to supply the hepatocytes. At each of the six corners of the lobule is a portal triad o Each has a SS Branch of the hepatic artery. Supplying oxygen rich arterial blood to the liver Branch of the hepatic portal vein. Carrying venous blood laden w / nutrients from the digestive system Bile duct. In between the plates are liver sinusoids, leaky permeable capillaries o Blood from the hepatic portal vein and hepatic artery percolate through sinusoids to the central vein The structure of the liver lobule is essential to the filtering process. Nutrient rich blood from the small intestine comes to the liver trough the hepatic portal vein and oxygen rich blood comes through the hepatic artery.

This blood flows b / w the plates of hepatocytes through sinusoid so Macrophages, Kupffer cells, that line the sinusoid walls pull out bacteria, cell debris, and worn out RBC so At the same time, hepatocytes pull out glucose, string it together as glycogen and store it until the blood sugar drops Also pull out amino acids needed for making albumin and clotting proteins Fat soluble vitamins (A DEK) are pulled out and stored Some toxic substances and drugs are pulled out too. Eventually blood flows through the sinusoids to the central vein o Empties to the hepatic vein o Empties to the inferior vena cava o Goes back to the heart Structure of liver lobule is also essential to digestion of lipid. Hepatocytes make bile. Bile flows through tiny canals called bile canaliculi that run b / w adjacent hepatocytes toward the bile duct in the portal triad o Run opposite of blood flow. All the bile ducts in the portal triads merge together to two major bile ducts (right and left). Right and left bile duct merge to the common hepatic duct.

Bile leaves the liver through the common hepatic duct and is brought straight down to the small intestine. Empties into the small intestine at the -pancreatic sphincter o Unless you eat fat and the appropriate hormones are present, the sphincter is close do Bile backs up if it is closed into the cystic duct of the gallbladder Gallbladder stores bile and concentrates it by pulling out water Stored for when you do eat fat and the appropriate hormones are present. SS Composition of Bile. Necessary for fat digestion. Chyme from the stomach, liquids and food you take in are high in water Lipids are hydrophobic to they get together in larges masses (globules) such that only the lipids on the outside have contact w / water PROBLEM is that enzymes have a tough time getting to the lipids in the middle that are buried b / c not a lot of surface area to work on. Bile has bile salts made from cholesterol o Allow emulsification o Pull apart the glob of lipid and encircle the pieces of the lipid to prevent them from adhering together again Now it is easier for enzymes to get at lipids for digestion.

Bile salts enter the duodenum of the small intestine by the sphincter and are reclaimed at the end of the small intestine o Re-used over and over. Also has cholesterol which goes to the small intestine and is secreted in feces o Too much forms crystals in the biliary calculi of the gallbladder causing gall stones. Pigment of bile is bilirubin o Breakdown product of hemoglobin Hub breaks to. Heme.

Amino acids-reused. Fe-used in new Hg bSS Heme portion breaks to bilirubin which goes to liver is added to bile and breaks to (by bacteria) giving feces its red-brown color If you have a problem getting bile to the small intestine, feces are gray b / c there is no bilirubin in them and no fat breakdown SS Lipids are digested from the beginning to the end of the small intestine. Pancreaso Secretes pancreatic juice to the small intestine o Released through the pancreatic duct that fuses w / the bile duct as it enters the duodenum o Has enzymes that can digest Proteins SS Lipids SS CHOSS Nucleic acid so Enzymes are inactivated till in the small intestine so that they cannot destroy the pancreas In small intestine, enzymes clip off a piece of the pancreatic enzyme to active it Others may need a vitamin to be activate do Bicarbonate ions are also in pancreatic juice To neutralize HCl in duodenum from stomach Bring pH to the alkaline range Digestive Process in the Small intestine. Chyme moves through the small intestine in 3-6 hours by segmentation o Back and forth movement Contraction that pushes contents forward, then another contraction pushes the contents backward, then forward again Functions to further break down food by mixing it w / pancreatic juices and bile. After most of the food is digested and nutrients are absorbed, start to have peristaltic waves in the small intestine o Begin at the duodenum and move to the ileum o Clears out what is left after absorption to the large intestine. Gastrin relaxes the sphincter b / w the small intestine and the large intestine (sphincter) o Is a hormone released w / peristaltic waves.

Large Intestine 4.5 feet long Diameter = 7 meter so Some water is absorbed here Real function is to move the residue of digestion out as feces o Subdivisions SS Cecum. Just below the sphincter Vermiform appendix. Attached to the surface of the cecum. Lymphoid tissue that prevents bacteria from getting to blood. Its twisted structure, however, is a ideal location for enteric bacteria to accumulate and multiply Colon. Has several distinct region so Up right side of body is ascending o Turns and goes across body transverse o Turns down on left side descending o Across again as the sigmoid o Down again as the rectum o Last segment is the anal canal Passageway to outside is the anus.

The anal canal has two sphincter so Interior anal sphincter Smooth muscle that you have no control over Exterior anal sphincter Skeletal muscle that you have control over Large intestine is lines w / simple columnar epithelium w / lots of goblet cell so Anal canal is stratified squamous epithelium b / c most of the water has been absorbed and material is dry and abrasive The anal canal needs more protection from friction o No digestive enzymes in the large intestine o No specializations for absorption (no villi or micro villi) SS Only water and vitamins are absorbed o Unusual things Longitudinal muscle layer of muscularis is only three strips of smooth muscle outside the circular layer and is called the tenia e coli. Not in the rectum (terminal end). Present in the Ascending Descending Transverse Sigmoid. Contraction of tenia e coli cause the intestine to pucker into pocket like sacs called haus traSS Epiploic appendages are small fat filled pouches of visceral peritoneum hanging from the surface of the large intestine.

No one knows why they are the reo Bacterial flora in the large intestine Make B-complex vitamin Make most of the vitamin-K the liver needs to synthesize clotting protein so Digestive function Harvests vitamins made by the bacterial flora Reclaims most of the remaining water Reclaims some electrolytes; particularly Na and Clo Major function is to remove waste from the body Does this by mass movements. Three or four times a day peristaltic waves push material to the rectum. As more is pushed the walls of the sigmoid and rectum stretch causing the defecation reflex o Parasympathetic reflex that causes the sigmoid colon and rectum to contract and the anal sphincters to relax. o As feces are forced into the anal canal, messages reach the brain allowing us to decide whether the external anal sphincter should remain open or be constricted to stop feces passage If defecation is delayed, the reflex contractions end w / in a few seconds and rectal walls relax W / next mass movement the defecation reflex is initiated again. DIGESTION OF MATERIALS. CHO: breaks to monosaccharides (glucose, fructose) o In the mouth by salivary amylase secreted by the salivary gland so In the small intestine by Pancreatic enzymes Brush border enzymes o Absorbed in by active transport in the capillaries of the small intestine. Proteins: break to amino acid so In the stomach by pepsin from the chief cell so In the small intestine by Pancreatic enzymes Brush border enzyme so Absorbed by active transport by the capillaries of the small intestine.

Lipids In the small intestine by pancreatic enzymes (lipases) o Break to SS Glycerol. Not used until in the blood Fatty acids. Go to the epithelial lining and packaged into Lipid, protein, cholesterol. Goes to lymphatic system Absorbed by the lacteals of the small intestine.

Vitamins Absorbed in the small intestine o Absorbed in the large intestine B and K. Water Absorbed mostly in the small intestine o Small amounts absorbed in the large intestine.