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Digestive Powerpoint Presentation Transcript

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