DIGESTIVE SYSTEM
ANATOMICAL OVERVIEW <ul><li>2 main groups of organs: </li></ul><ul><li>Alimentary canal (Gastrointestinal or GI tract) </l...
ANATOMICAL OVERVIEW <ul><li>GENERAL ANATOMICAL FEATURES OF THE DIGESTIVE SYSTEM </li></ul>
Alimentary Canal – mouth <ul><li>Food enters through the mucous-lined  mouth  or  oral cavity </li></ul><ul><li>Lips (labi...
<ul><li>Oral cavity proper  – area contained by the teeth </li></ul><ul><li>Tongue  – muscular tissue attached to hyoid bo...
Alimentary Canal – pharynx <ul><li>Divided into 3 distinct sections: </li></ul><ul><ul><li>Nasopharynx  – not involved in ...
Alimentary Canal – esophagus <ul><li>The esophagus ( gullet ) is basically a connecting tube between the mouth and the sto...
Alimentary Canal – stomach <ul><li>Stomach  – found on left side of abdominopelvic cavity </li></ul><ul><li>Regions of the...
Stomach - continued <ul><li>The stomach is about 10in. In length, but its diameter is dependent upon fullness (can hold  4...
Stomach - continued <ul><li>Stomach cells also secrete or produce: </li></ul><ul><ul><li>Intrinsic factor  – needed for ab...
Stomach - continued
Alimentary Canal - small intestines <ul><li>Small intestines are where most digestion and absorption takes place </li></ul...
Small Intestine - continued <ul><li>3 subdivisions: </li></ul><ul><ul><li>Duodenum  – shortest part; place where pancreati...
Small Intestine - continued <ul><li>Nearly all food and nutrient absorption takes place in the small intestines. 3 main st...
Small Intestine - continued <ul><li>Microvilli  – tiny projections of mucosa cells that create a fuzzy surface referred to...
Alimentary Canal – large intestines <ul><li>Begin at the ileocecal valve; Bigger in diameter than the small intestines, bu...
Large Intestines - continued <ul><li>Cecum  – 1 st  part of large intestines; has the appendix attached to it via mesentar...
Large Intestines - continued <ul><li>Contains many  goblet cells  in the mucosa that produce an alkaline mucus to lubricat...
Accessory Digestive Organs <ul><li>SALIVARY GLANDS </li></ul><ul><li>3 sets: </li></ul><ul><ul><li>Parotid  – large, anter...
Accessory Digestive Organs <ul><li>TEETH </li></ul><ul><li>Deciduous, baby, or milk teeth </li></ul><ul><ul><li>Begin to e...
Accessory Digestive Organs <ul><li>TEETH (CONTINUED) </li></ul><ul><li>2 regions – crown & root </li></ul><ul><li>Crown  i...
Accessory Digestive Organs <ul><li>PANCREAS </li></ul><ul><li>Soft, pink, triangular gland, extends from spleen to duodenu...
Accessory Digestive Organs <ul><li>LIVER </li></ul><ul><li>Largest gland in the body, located under the diaphragm and more...
ANATOMICAL OVERVIEW <ul><li>GALLBLADDER </li></ul><ul><li>Small, thin-walled green sac found on the inferior surface of th...
PHYSIOLOGY <ul><li>OVERVIEW OF GI PROCESSES & CONTROLS </li></ul><ul><li>Ingestion </li></ul><ul><li>Propulsion </li></ul>...
PHYSIOLOGY <ul><li>ACTIVITIES OF THE MOUTH, PHARYNX, & ESOPHAGUS </li></ul><ul><li>Food ingestion & breakdown </li></ul><u...
PHYSIOLOGY <ul><li>ACTIVITIES OF THE STOMACH </li></ul><ul><li>Food breakdown </li></ul><ul><ul><li>Mechanical Digestion –...
PHYSIOLOGY <ul><li>ACTIVITIES OF THE SMALL INTESTINES </li></ul><ul><li>Food breakdown </li></ul><ul><ul><li>Mechanical di...
PHYSIOLOGY <ul><li>ACTIVITIES OF THE LARGE INTESTINES </li></ul><ul><li>Food Breakdown </li></ul><ul><ul><li>Mechanical di...
PHYSIOLOGY
PHYSIOLOGY
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Digestive Powerpoint

  1. 1. DIGESTIVE SYSTEM
  2. 2. ANATOMICAL OVERVIEW <ul><li>2 main groups of organs: </li></ul><ul><li>Alimentary canal (Gastrointestinal or GI tract) </li></ul><ul><ul><li>Made up of the mouth, pharynx, esophagus, stomach, small intestines, and large intestines (anus) </li></ul></ul><ul><ul><li>Responsible for ingestion, digestion, absorption, and defecation </li></ul></ul><ul><ul><li>Hollow tube open at both ends </li></ul></ul><ul><li>Accessory digestive organs </li></ul><ul><ul><li>Made up of teeth, tongue, salivary glands, pancreas, liver, and gallbladder </li></ul></ul><ul><ul><li>Responsible for assisting in both mechanical and chemical breakdown of ingested food </li></ul></ul>
  3. 3. ANATOMICAL OVERVIEW <ul><li>GENERAL ANATOMICAL FEATURES OF THE DIGESTIVE SYSTEM </li></ul>
  4. 4. Alimentary Canal – mouth <ul><li>Food enters through the mucous-lined mouth or oral cavity </li></ul><ul><li>Lips (labia) – protection </li></ul><ul><li>Cheeks – lateral walls </li></ul><ul><li>Hard & soft palate – anterior & posterior roof respectively </li></ul><ul><li>Vestibule – space between lips & cheeks as well as teeth & gums </li></ul>
  5. 5. <ul><li>Oral cavity proper – area contained by the teeth </li></ul><ul><li>Tongue – muscular tissue attached to hyoid bone and styloid processes; involved in speech & swallowing; papillae contain taste buds </li></ul><ul><li>Lingual frenulum – small fold that anchors tongue; associated with some speech impediments </li></ul><ul><li>Palatine and lingual tonsils - paired lymphatic tissue masses in posterior of oral cavity; defend against pathogens; make swallowing difficult when infected or inflamed </li></ul><ul><li>Mastication - chewing </li></ul>Mouth - continued
  6. 6. Alimentary Canal – pharynx <ul><li>Divided into 3 distinct sections: </li></ul><ul><ul><li>Nasopharynx – not involved in the digestive system </li></ul></ul><ul><ul><li>Oropharynx – found directly in the back of the oral cavity </li></ul></ul><ul><ul><li>Laryngopharynx – most inferior portion, leads into the esophagus; also where pharynx splits into esophagus and trachea (epiglottis) </li></ul></ul><ul><li>Contains two different skeletal muscle layers: </li></ul><ul><ul><li>Inner layer – longitudinal </li></ul></ul><ul><ul><li>Outer layer – circular </li></ul></ul><ul><ul><li>Alternating contractions of these muscles propels food down toward stomach ( peristalsis ) </li></ul></ul>
  7. 7. Alimentary Canal – esophagus <ul><li>The esophagus ( gullet ) is basically a connecting tube between the mouth and the stomach (about 10in.) </li></ul><ul><li>Lining of walls consists of 4 different layers: </li></ul><ul><ul><li>Mucosa – inner most layer; lines lumen (cavity) </li></ul></ul><ul><ul><ul><li>Epithelium – stratified squamous (friction) & simple columnar </li></ul></ul></ul><ul><ul><ul><li>Connective tissue </li></ul></ul></ul><ul><ul><ul><li>Smooth muscle </li></ul></ul></ul><ul><ul><li>Submucosa – soft CT; contains blood & lymph vessels, lymph nodes, & nerve endings </li></ul></ul><ul><ul><li>Muscularis externa – smooth muscle layer (inner = circular, outer = longitudinal….this is opposite of the muscles found in the pharynx) </li></ul></ul><ul><ul><li>Serosa – outermost layer, only a single layer of cells thick </li></ul></ul><ul><ul><ul><li>Cells secrete serous fluid and the layer is called visceral peritoneum </li></ul></ul></ul><ul><ul><ul><li>Connects to parietal peritoneum (part of mesentary ) that lines abdominopelvic cavity </li></ul></ul></ul>
  8. 8. Alimentary Canal – stomach <ul><li>Stomach – found on left side of abdominopelvic cavity </li></ul><ul><li>Regions of the stomach: </li></ul><ul><ul><li>Cardiac – surrounds cardioesophageal sphincter (valve through which food enters from the esophagus </li></ul></ul><ul><ul><li>Fundus – expanded part of the stomach </li></ul></ul><ul><ul><li>Body – midportion </li></ul></ul><ul><ul><li>Pyloric antrum – narrowing </li></ul></ul><ul><ul><li>area inferior to body </li></ul></ul><ul><ul><li>Pylorus – funnel-shaped </li></ul></ul><ul><ul><li>terminal part that leads to </li></ul></ul><ul><ul><li>small intestines via the </li></ul></ul><ul><ul><li>pyloric sphincter </li></ul></ul>
  9. 9. Stomach - continued <ul><li>The stomach is about 10in. In length, but its diameter is dependent upon fullness (can hold 4L or 1 gallon of food) </li></ul><ul><li>When less full or empty, it collapses inward creating folds called rugae </li></ul><ul><li>Greater curvature – convex lateral side </li></ul><ul><li>Lesser curvature – concave medial side </li></ul><ul><li>Acts as a temporary “storage tank” & site for food breakdown </li></ul><ul><li>Contains a 3 rd set of muscles called the muscularis externa that run obliquely and churn the food as it moves along (physical or mechanical breakdown) </li></ul><ul><li>Chemical breakdown of proteins starts in the stomach </li></ul><ul><li>Mucosa is simple columnar epithelium lined with gastric pits that lead to gastric glands </li></ul><ul><ul><li>Gastric glands secrete gastric juice </li></ul></ul>
  10. 10. Stomach - continued <ul><li>Stomach cells also secrete or produce: </li></ul><ul><ul><li>Intrinsic factor – needed for absorption of vitamin B 12 by the small intestines </li></ul></ul><ul><ul><li>Chief cells – protein-digesting enzymes ( pepsinogens ) </li></ul></ul><ul><ul><li>Parietal cells – hydrochloric acid (HCl) used for chemical digestion (activates other enzymes) </li></ul></ul><ul><ul><li>Mucous neck cells – alkaline mucus to protect stomach lining </li></ul></ul><ul><ul><li>Enteroendocrine cells – local hormones (not part of endocrine system) like gastrin </li></ul></ul><ul><li>Pyloric region is most active for digestion – the partially digested and broken down food that leaves the stomach is called chyme </li></ul><ul><li>Pyloric sphincter – valve that opens to allow chyme to pass into small intestines </li></ul>
  11. 11. Stomach - continued
  12. 12. Alimentary Canal - small intestines <ul><li>Small intestines are where most digestion and absorption takes place </li></ul><ul><li>Extend from the pyloric sphincter to the ileocecal valve </li></ul><ul><li>Longest part of the GI tract; 8-18 ft. (absorption); held together and supported in the abdominal cavity by mesentary </li></ul>
  13. 13. Small Intestine - continued <ul><li>3 subdivisions: </li></ul><ul><ul><li>Duodenum – shortest part; place where pancreatic enzymes (pancreatic ducts) and bile (bile ducts) enter the intestines </li></ul></ul><ul><ul><li>Jejunum – middle portion of intestines </li></ul></ul><ul><ul><li>Ileum – makes up over half of the length of the small intestines; joins with the large intestines at the ileocecal valve </li></ul></ul>
  14. 14. Small Intestine - continued <ul><li>Nearly all food and nutrient absorption takes place in the small intestines. 3 main structures account for the increased absorptive abilities: </li></ul><ul><li>Microvilli </li></ul><ul><li>Villi </li></ul><ul><li>Circular folds </li></ul>
  15. 15. Small Intestine - continued <ul><li>Microvilli – tiny projections of mucosa cells that create a fuzzy surface referred to as a “ brush border .” </li></ul><ul><ul><li>These projections cover the surface of the villi </li></ul></ul><ul><li>Villi – fingerlike projections of the mucosa that contain: </li></ul><ul><ul><li>Capillary beds </li></ul></ul><ul><ul><li>Lymphatic capillaries called lacteals </li></ul></ul><ul><ul><li>Both of these structures receive digested foodstuff through diffusion </li></ul></ul><ul><li>Circular folds (plicae circularis) – folded parts of the mucosa and submucosa layers that creates more surface area (=more absorption) </li></ul><ul><li>Peyer’s patches (from lymphatic unit) are found in large numbers near the end of the small intestines – help rid leftover undigested foodstuff of bacteria </li></ul>
  16. 16. Alimentary Canal – large intestines <ul><li>Begin at the ileocecal valve; Bigger in diameter than the small intestines, but only about 5ft in length and therefore much shorter </li></ul><ul><li>Shorter length due to function: </li></ul><ul><ul><li>only things absorbed are water & some vitamins (B & K) </li></ul></ul><ul><li>SUBDIVISIONS: </li></ul><ul><li>Cecum </li></ul><ul><li>Appendix </li></ul><ul><li>Colon (4 parts) </li></ul><ul><li>Rectum </li></ul><ul><li>Anal canal </li></ul>
  17. 17. Large Intestines - continued <ul><li>Cecum – 1 st part of large intestines; has the appendix attached to it via mesentary </li></ul><ul><li>Appendix – believed at one time to help digest cellulose; new evidence suggests is houses “good” bacteria that can replenish those lost due to diseases such as cholera and amebic dysentary </li></ul><ul><ul><li>Inflammation – appendicitis (“bad” bacteria take over); appendectomy </li></ul></ul><ul><li>Colon: </li></ul><ul><ul><li>Ascending – up the right side </li></ul></ul><ul><ul><li>Transverse – across the abdominal cavity </li></ul></ul><ul><ul><li>Descending – down the left side </li></ul></ul><ul><ul><li>Sigmoid – s-shaped, found in pelvic region </li></ul></ul><ul><li>Rectum and anal canal – lead to the anus and contain 2 sphincters: internal = smooth muscle (involuntary); external skeletal muscle (voluntary) </li></ul>
  18. 18. Large Intestines - continued <ul><li>Contains many goblet cells in the mucosa that produce an alkaline mucus to lubricate and raise the pH of fecal matter passing through it </li></ul><ul><li>Longitudinal muscles of the muscularis external called teniae coli create small pocketlike sections called haustra </li></ul>
  19. 19. Accessory Digestive Organs <ul><li>SALIVARY GLANDS </li></ul><ul><li>3 sets: </li></ul><ul><ul><li>Parotid – large, anterior to ears, inflammation causes mumps </li></ul></ul><ul><ul><li>Submandibular </li></ul></ul><ul><ul><li>Sublingual </li></ul></ul><ul><li>Make saliva – mixture of mucus and serous fluids </li></ul><ul><ul><li>Moistens and binds food into a mass called a bolus </li></ul></ul><ul><ul><li>Contains salivary amylase (enzymes) – breaks down starch (carbohydrates) </li></ul></ul><ul><ul><li>Lysozyme and IgA antibodies – protect against bacteria </li></ul></ul><ul><ul><li>Dissolves food so it can be tasted </li></ul></ul>
  20. 20. Accessory Digestive Organs <ul><li>TEETH </li></ul><ul><li>Deciduous, baby, or milk teeth </li></ul><ul><ul><li>Begin to erupt at 6 months, full set of 20 by 2 years </li></ul></ul><ul><ul><li>Begin to fall out between 6-12 yrs old </li></ul></ul><ul><li>Permanent teeth </li></ul><ul><ul><li>All but 3 rd molars (wisdom teeth) are erupted by end of adolescence </li></ul></ul><ul><li>Incisors – chisel-shaped, cutting </li></ul><ul><li>Canines – eyeteeth, fangs, tearing or piercing </li></ul><ul><li>Premolars (bicuspids) & molars - grinding </li></ul>
  21. 21. Accessory Digestive Organs <ul><li>TEETH (CONTINUED) </li></ul><ul><li>2 regions – crown & root </li></ul><ul><li>Crown is exposed part above the gingiva ( gums ); covered by enamel (hard but brittle) </li></ul><ul><li>Root – embedded in the jawbone and connected to crown by neck </li></ul><ul><ul><li>Cementum </li></ul></ul><ul><ul><li>Periodontal membrane </li></ul></ul><ul><ul><li>Dentin </li></ul></ul><ul><ul><li>Pulp cavity </li></ul></ul><ul><ul><li>Pulp </li></ul></ul><ul><ul><li>Root canal </li></ul></ul>
  22. 22. Accessory Digestive Organs <ul><li>PANCREAS </li></ul><ul><li>Soft, pink, triangular gland, extends from spleen to duodenum, retroperitoneal </li></ul><ul><li>Produces enzymes that break down all categories of digestible foods; pancreatic enzymes are secreted into the duodenum in an alkaline fluid , which neutralizes the acidic chyme coming from the stomach; also involved in endocrine activity (insulin & glucagon) </li></ul>
  23. 23. Accessory Digestive Organs <ul><li>LIVER </li></ul><ul><li>Largest gland in the body, located under the diaphragm and more toward the right side of the body, made up of 4 lobes </li></ul><ul><li>Major digestive function is to produce bile </li></ul><ul><ul><li>Bile – yellow/green watery solution that contains bile salts, bile pigments such as bilirubin (used to breakdown hemoglobin), cholesterol, phospholipids, and various electrolytes </li></ul></ul><ul><ul><ul><li>Bile salts emuslify fats by breaking down large fat globules into smaller ones (increases surface area so enzymes can break it down more, faster) </li></ul></ul></ul><ul><ul><ul><li>Bile is secreted out of the liver through the common hepatic duct and into the duodenum through the bile duct </li></ul></ul></ul><ul><li>Liver also plays a role in metabolic and regulatory bodily activities </li></ul>
  24. 24. ANATOMICAL OVERVIEW <ul><li>GALLBLADDER </li></ul><ul><li>Small, thin-walled green sac found on the inferior surface of the liver. </li></ul><ul><ul><li>Cystic duct – collects excess bile that builds up when food digestion is not taking place. </li></ul></ul><ul><ul><li>The backed-up bile empties into the gallbladder and water is removed to make the bile very concentrated. </li></ul></ul><ul><ul><li>When fatty foods enter into the duodenum, a hormonal signal is sent to the gallbladder to release the bile to help break down the fat in the duodenum </li></ul></ul>
  25. 25. PHYSIOLOGY <ul><li>OVERVIEW OF GI PROCESSES & CONTROLS </li></ul><ul><li>Ingestion </li></ul><ul><li>Propulsion </li></ul><ul><li>Mechanical digestion </li></ul><ul><li>Chemical digestion </li></ul><ul><li>Absorption </li></ul><ul><li>Defecation </li></ul>
  26. 26. PHYSIOLOGY <ul><li>ACTIVITIES OF THE MOUTH, PHARYNX, & ESOPHAGUS </li></ul><ul><li>Food ingestion & breakdown </li></ul><ul><ul><li>Mechanical digestion – mastication </li></ul></ul><ul><ul><li>Chemical breakdown – salivary amylase (carbohydrates) </li></ul></ul><ul><li>Food propulsion </li></ul><ul><ul><li>Swallowing ( deglutition ) consists of 2 phases </li></ul></ul><ul><ul><ul><li>Buccal phase - voluntary, bolus is swallowed </li></ul></ul></ul><ul><ul><ul><li>Pharyngeal-esophageal phase – involuntary (parasympathetic) </li></ul></ul></ul><ul><ul><li>Propulsion occurs by peristalsis of smooth muscles of the pharynx & esophagus </li></ul></ul><ul><ul><li>Uvula blocks off nasopharynx, epiglottis blocks off larynx so food can only enter into esophagus </li></ul></ul>
  27. 27. PHYSIOLOGY <ul><li>ACTIVITIES OF THE STOMACH </li></ul><ul><li>Food breakdown </li></ul><ul><ul><li>Mechanical Digestion – the combination of different muscle layers churn the food to mix & mash it (oblique layer) </li></ul></ul><ul><ul><li>Chemical Digestion – secretion of gastric juices is both neural & hormonal. </li></ul></ul><ul><ul><ul><li>Senses stimulate the parasympathetic nervous system to secrete more gastric juice </li></ul></ul></ul><ul><ul><ul><li>Presence of food in the stomach causes a drop in pH, stimulating more production of pesinogens & HCL </li></ul></ul></ul><ul><li>Absorption </li></ul><ul><ul><ul><li>Aspirin & alcohol are some of the very few items absorbed in the stomach </li></ul></ul></ul><ul><li>Food propulsion </li></ul><ul><ul><li>Muscle action pushes the mixed up chyme toward the pylorus to enter into the small intestines through the pyloric sphincter. </li></ul></ul><ul><li>4-6 hours in the stomach </li></ul>
  28. 28. PHYSIOLOGY <ul><li>ACTIVITIES OF THE SMALL INTESTINES </li></ul><ul><li>Food breakdown </li></ul><ul><ul><li>Mechanical digestion – continues by the process of peristalsis, but otherwise is pretty much complete. </li></ul></ul><ul><ul><li>Chemical digestion – acidic chyme that enters the duodenum is neutralized by bicarbonate enzymes </li></ul></ul><ul><ul><ul><li>Bile released from the gallbladder also enters the small intestines at the duodenum. It initiates the breakdown of fat (lipid) molecules </li></ul></ul></ul><ul><li>Absorption </li></ul><ul><ul><li>Main function of the small intestines (reason for its length) </li></ul></ul><ul><ul><li>Absorption of water and most nutrients is done through active transport (requires energy) and enters the capillary beds to be carried to the liver </li></ul></ul><ul><ul><li>Absorption of fats occurs by diffusion (no energy needed) enters both capillaries & lacteals to be transported to the liver </li></ul></ul><ul><li>3-6 hours </li></ul>
  29. 29. PHYSIOLOGY <ul><li>ACTIVITIES OF THE LARGE INTESTINES </li></ul><ul><li>Food Breakdown </li></ul><ul><ul><li>Mechanical digestion – none really, just removal of water from the fecal matter </li></ul></ul><ul><ul><li>Chemical breakdown – no digestive enzymes produced, but bacteria help breakdown some indigestible foods such as cellulose. </li></ul></ul><ul><ul><ul><li>These bacteria are also responsible for fecal odor and gas (flatulence) since they create methane as a waste product of their metabolism </li></ul></ul></ul><ul><ul><ul><li>The bacteria also produce some vitamins such as B & K that can be absorbed by the large intestines </li></ul></ul></ul><ul><li>Propulsion </li></ul><ul><ul><li>Segmentation & peristalsis (haustra) (3-4 powerful contractions/day) </li></ul></ul><ul><li>Defecation </li></ul><ul><ul><li>Wall of sigmoid colon & anal canal stretches, sending message to brain & initiating the defecation reflex </li></ul></ul>
  30. 30. PHYSIOLOGY
  31. 31. PHYSIOLOGY

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