Ann Senisi Scott & Elizabeth Fong: Body Structures & Functions 11 th Edition

Transcription

1 Chapter 18: Digestive System Thery Lecture Outline Objectives 1. Describe the general functin f the digestive system 2. List the structures and the functins f the digestive system 3. Describe the actin f the enzymes n carbhydrates, fats and prtein 4. Trace fd frm the beginning f the digestive prcess t the end 5. Describe cmmn disrders f the digestive system 6. Define the key wrds that relate t this chapter Intrductin The functin f the digestive system is t prcess fd int mlecules that can be absrbed and used by the cells f the bdy. Fd is brken dwn, bit by bit, until the mlecules are small enugh t be absrbed and the waste prducts are eliminated. Digestive System Fd must be cnverted by physical and chemical changes befre it can be used by the cells; this prcess is called digestin Enzymes are chemical substances that prmte chemical reactins in living things The digestive system includes the alimentary canal, als knwn as the digestive tract r gastrintestinal (GI) tract, and its accessry rgans Alimentary canal a. Organs include: 1. Muth (ral cavity) 2. Pharynx (thrat) 3. Esphagus (gullet) 4. Stmach 5. Small intestine 6. Large intestine (cln) 7. Anus b. The alimentary canal is a cntinuus tube sme 30 feet in length frm the muth t anus Accessry rgans a. Tngue b. Teeth c. Salivary glands d. Pancreas e. Liver f. Gallbladder Layers f the Digestive System The walls f the alimentary canal are cmpsed f fur layers Mucsa a. Innermst lining is made up f epithelial cells b. Certain cells in the mucsa secrete mucus, digestive enzymes and hrmnes Mucus lubricates aiding in the passage f fd c. Als insulates the digestive tract frm the effects f pwerful enzymes Submucsa Cnsists f cnnective tissue with fibers, bld vessels and nerve endings Circular muscle Lngitudinal muscle

2 Lining f the Digestive System Peritneum Serus membrane that lines the abdminal cavity a. Tw-layered membrane 1. Parietal Lines the abdminal cavity 2. Visceral Cvers the utside f each rgan in the abdminal cavity b. Specialized layers 1. Mesentery 2. Greater mentum Functins f the Digestive System Break dwn fd physically int smaller pieces Change fd chemically Absrb the nutrients Eliminate the waste prducts f digestin Attaches t the psterir wall f the abdminal cavity and the small intestines Cntains large amunts f fat and hangs ver the abdminal rgans like a prtective aprn Organs f Digestin Many rgans cntribute t digestin; each serving a specific functin in the prcess Muth (ral r buccal cavity) a. First part f the digestive tract b. Functins 1. Receive fd by ingestin 2. Break fd int small particles by masticatin 3. Mix fd with saliva c. Uvula 1. Cne-shaped flap f tissue that hangs frm the middle f the sft palate 2. Prevents fd frm entering the nasal cavity when swallwing Tngue/accessry rgan f digestin a. The tngue and its muscles are attached t the flr f the muth, helping in bth chewing and swallwing b. Made frm skeletal muscles that lie in many different planes allwing mvement in varius directins c. Papillae 1. Prjectins lcated n the surface 2. Cntain nerve endings, frming the sense rgans f taste, r taste buds Bitterness, saltiness, sweetness and surness Als sensitive t cld, heat and pressure The sensatin f taste is cupled with the sense f smell Salivary glands a. Three pairs f salivary glands secrete saliva int the ral cavity 1. Partid (in frnt and belw the ears) 2. Submandibular (lwer jaw) 3. Sublingual (under the sides f the tngue) b. Functins f saliva 1. Cleansing actin n the teeth 2. Mistens and lubricates fd during masticatin and swallwing 3. Disslves certain mlecules s that fds can be tasted 4. Begins the chemical digestin f starches

3 Teeth/Accessry Organ f Digestin Gingivae r gums a. Supprt and prtect the teeth b. Surrunds the narrw prtins f the teeth and cvers the structures in the upper and lwer jaws Teeth a. Fd chewed r masticated Breaks fd dwn and enables the digestive enzymes t digest the fd mre efficiently and quickly b. Deciduus and permanent teeth Figure 18-5 pg deciduus teeth (10 in each jaw) that may last up t the age f 12 incisrs (sharp edges fr biting) canines (pinted fr tearing) mlars (ridges fr crushing and grinding) permanent teeth (16 in each jaw) 8 incisrs 4 canines 8 premlars (bicuspids fr grinding) 12 mlars Structure f the tth a. Three majr parts 1. Crwn (visible prtin f the tth) 2. Neck (where the tth enters the gumline) 3. Rt (prtin that is embedded in the jaw) b. Pulp cavity 1. Inside f tth 2. Cntains nerves and bld supply Esphagus Muscular tube t transprt swallwed fd t stmach a. Lies behind the trachea and in frnt f the vertebral clumn b. Passes thrugh an pening in the diaphragm and then empties int the stmach Muscles in the upper third are vluntary and lwer prtin is smth muscle, r invluntary Stmach Lcated in the upper part f the abdminal cavity, just t the left f and belw the diaphragm Divided int 3 prtins a. Fundus Upper part b. Bdy r great curvature Middle sectin c. Pylrus Lwer prtin Sphincters a. Cardiac sphincter b. Pylric sphincter Fur layers f the stmach wall a. Mucus, submucus, muscular and serus layers b. The muscular layer in the wall f the stmach prvides mixing mvements t mix the fd with enzymes and ther fluids; when the stmach is empty, the mucsa and submucsa exhibit lngitudinal flds, called rugae (r-jee); these flds allw the stmach t expand, and as it fills the rugae becmes less apparent

4 Gastric Juices The gastric mucsa cntains millins f gastric glands which secrete gastric juice necessary fr digestin Enterendcrine glands Secrete gastrin hrmne that stimulates gastric gland secretin Parietal cells Chief type cells Mucus cells Prduces HCL (hydrchlric acid) which kills bacteria and intrinsic factr which facilitates the absrptin f vitamin B 12 Prduce pepsingen (active frm f pepsin) which begins digestin f prteins int plypeptides Secrete alkaline mucus which helps neutralize the effects f HCL acid and the ther digestive juices Small Intestine Abut 20 feet lng Same fur layers as the stmach Divided int 3 sectins a. Dudenum b. Jejunum c. Ileum Functins a. Finishes the prcess f digestin b. Absrbs the nutrients c. Passes the residue n t the large intestine Digestive Juices in the Small Intestine The cmbined actin f pancreatic juice, bile and intestinal juice cmpletes the prcess f changing carbhydrates first int starch then int glucse, prtein int amin acids and fats int fatty acids and glycerl Enzymes, secretin, and chlecystkinin Stimulate the digestive juices f the pancreas, liver and gallbladder Pancreatic juices a. Prtease r trypsin break dwn prteins t amin acids b. Amylase r amylpsin break dwn starches t glucse c. Lipase r steapsin break dwn fats t fatty acids and glycerl Bile Necessary t break dwn r emulsify fat int smaller fat glbules t be digested by lipase and steapsin Intestinal juices a. Maltase, lactase and sucrase change starch int glucse b. Peptidase changes prtease and peptne int amin acids c. Steapsin changes fat int fatty acids and glycerl Absrptin in the Small Intestine Villi Makes absrptin pssible Each villi cntains a netwrk f bld and lymph capillaries Digested prtin passes thrugh the villi int the bldstream and lacteals Undigested prtin passes n t the large intestine Accessry Organs f Digestin Pancreas a. Feather-shaped rgan lcated behind the stmach

5 b. Functins bth as an excrine and as an endcrine 1. Endcrine islets f Langerhans secretes the hrmnes insulin and glucagn int the bld 2. Excrine secretes digestive enzymes frm the pancreatic duct int the dudenum Liver a. Largest rgan in the bdy b. Lcated belw the diaphragm, in the upper right quadrant f the abdmen c. Functins 1. Manufactures bile, a yellw t green fluid, which is necessary fr the digestin f fat 2. Prduce and stre glucse in the frm f glycgen 3. Detxify harmful substances such as alchl and drugs 4. Manufacture bld prteins necessary fr bld cltting 5. Stre vitamins A, D and B cmplex 6. Cnverts ammnia int urea, chief waste prduct f prtein metablism 7. Break dwn hrmnes n lnger useful 8. Remve wrn-ut red bld cells frm circulatin and recycle the irn cntent Gallbladder a. Small green rgan in the inferir surface f the liver b. Functin is t stre and cncentrate bile when it is nt needed by the bdy Large Intestine Begins at the ilececal junctin, where the ileum enters the large intestine, and ends at the anus Als called the cln Abut 5 feet lng Ileum empties chyme (semi-liquid fd) thrugh ilececal valve int large intestine Regins f the large intestine a. Cecum and appendix 1. Cecum is a blind puch that extends frm the ilececal junctin 2. Vermifrm appendix is attached t the cecum and has n digestive functin (cntains lymphatic tissue) b. Ascending, transverse, and descending cln Frames the abdmen c. Sigmid cln S-shaped curve that becmes the rectum d. Anal canal Guarded by tw anal sphincters (internal sphincter is invluntary and the external sphincter is vluntary) Functins a. Absrptin f fluid and electrlytes and the eliminatin f waste prducts (prduces n digestive enzymes and has n villi fr the absrptin f nutrients) b. Mucus lubricates the passage f fecal material General Overview f Digestin Each part f the alimentary canal cntributes t the verall digestive prcess Muth a. Blus 1. Sft, pliable ball created frm saliva and the mechanical breakdwn f fd in the muth 2. Blus slides dwn the thrat (pharynx) t be swallwed b. Salivary glands begin chemical digestin f starches

6 Pharynx a. Swallwing, r deglutitin, is a cmplex prcess invlving the cnstrictr muscles f the pharynx b. Begins as a vluntary prcess, changes t an invluntary prcess as the fd enters the esphagus Esphagus Peristalsis 1. Fd is pushed alng the esphagus, stmach, small and large intestine by rhythmic, muscular cntractins called peristalsis 2. The nervus system stimulates gland activity and peristalsis Stmach a. HCL acid prepares the gastric area fr enzyme actin b. Pepsin breaks dwn prteins and lipase acts n emulsified fats c. The actin f the gastric juices is helped by the churning f the stmach walls Semiliquid fd is called chyme d. The nly knwn substances t be absrbed in the stmach are alchl and sme medicatins Small intestine a. Prcess f digestin is cmpleted and absrptin ccurs 1. Prtein (begins in the stmach) brken dwn int amin acids 2. Fats (small intestine) changed int fatty acids and glycerl 3. Carbhydrates (cmpleted in the small intestine) cnverted t simple sugars such as glucse b. Absrptin f nutrients Actin in the Large Intestine The large intestine is cncerned with water absrptin, bacterial actin, fecal frmatin, gas frmatin and defecatin a. Absrptin 1. Water is drawn frm the undigested fd and indigestible material that pass thrugh the cln 2. Vitamins B cmplex and K absrptin b. Bacterial actin 1. Intestinal bacteria are harmless t their hst 2. Act upn undigested fd remains, turning them int acids, amines, gases and ther waste prducts c. Gas frmatin Prduced by swallwed air and the nrmal breakdwn f fd d. Fecal frmatin 1. Feces cnsist f bacteria, waste prducts frm the bld, acids, amines, inrganic salts, gases, mucus and cellulse 2. Cellulse is the fibrus part f plants that humans are unable t digest; it cntributes t the bulk f the feces e. Defecatin Purpse f these functins is t regulate the bdy s water balance while string and excreting waste prducts f digestin Effects f Aging Decrease sensry ability f taste buds Reductin f saliva Lss f teeth Slwing peristalsis

7 Metablism After digestin and absrptin, nutrients are carried by the bld t the cells f the bdy Within the cells, nutrients are changed int energy Aerbic metablism nutrients are cmbined with xygen within each cell (knwn as xidatin) Anaerbic metablism reduces fats withut the use f xygen Thyrid hrmnes Metablism is gverned primarily by the hrmnes secreted by the thyrid gland Disrders Digestive System Stmatitis Inflammatin f the sft tissues f the muth cavity Gingivitis r gum disease Peridntal disease Chrnic bacterial infectin f the gums and surrunding tissue Gastresphageal reflux disease (GERD) Sphincter muscle is weak allwing stmach s cntents t flw up int the esphagus Heartburn Acid indigestin results frm a backflw f highly acidic gastric juice int the lwer end f the esphagus Hiatal hernia (rupture) Stmach prtrudes abve the diaphragm thrugh the esphagus pening Pylric stensis Narrwing f the pylric sphincter at the lwer end f the stmach Gastritis Acute r chrnic inflammatin n the stmach lining Gastrenteritis Inflammatin f the mucus membrane lining f the stmach and intestinal tract Enteritis Inflammatin f the intestine Ulcer Sre r lesin that frms in the mucsal lining f the stmach r dudenum where acid and pepsin are present Inflammatry bwel disease (IBD) Chrnic diarrhea pssibly due t an aut immune disease Appendicitis Inflamed vermifrm appendix Hepatitis Inflammatin f the liver Cirrhsis Chrnic, prgressive, inflammatry disease f the liver Chlecystitis Inflammatin f the gallbladder Gallstnes Chlelithiasis, cllectin f crystallized chlesterl in the gallbladder Pancreatitis Inflammatin f the pancreas Diverticulsis Cnditin in which little sacs (diverticula) develp in the wall f the cln Hemrrhids Cnditin in which the veins arund the anus r lwer rectum are swllen and inflamed Diarrhea Characterized by lse, watery and frequent bwel mvements Cnstipatin Cnditin in which defecatin is delayed due t excessive water absrptin