Digestion. Processing of food Types. Mechanical (physical) Chemical. Chew Tear Grind Mash Mix. Catabolic reactions Enzymatic hydrolysis

Transcription

1 Digestive System

2 Digestion Processing of food Types Mechanical (physical) Chew Tear Grind Mash Mix Chemical Catabolic reactions Enzymatic hydrolysis Carbohydrate Protein Lipid 2

3 Digestion Phases Ingestion Movement Digestion Absorption 3

4 Digestive System Organization Gastrointestinal (Gl) tract (Alimentary canal) Tube within a tube Direct link/path between organs Structures Mouth Oral Cavity Pharynx Esophagus Stomach Duedenum Jejenum kileum Cecum Ascending colon Transverse colon 4

5 Digestive System Organization Descending colon Sigmoid colon Rectum Anus Accessory structures Not in tube path Organs Teeth Tongue Salivary glands Liver Gall bladder Pancreas 5

6 Anatomy of the Mouth and Throat 6

7 The Major Salivary Glands 7

8 Major Salivary Glands Parotid gland(25%) is the largest of the three glands and is located below and in front of the ears, secretes a fluid rich in amylase Becomes infected and swollen with the mumps Submandibular Glands(70%) located in the floor of the mouth on the inside surface of the lower jaw Secretes mostly a serous fluid Sublingual glands(5%) Are the smallest of the salivary glands and is located on the floor of the mouth under the tongue. 8

9 Saliva-Functions and composition Saliva Functions Moistens the mouth Digest a little starch and fat Cleanses the teeth Inhibits bacterial growth Dissolves molecules so they can stimulate taste buds Dilute and buffer foods Moistens food and binds particles together to aid in swallowing(bolus formation) Saliva Composition Is a hypotonic solution of 99% water and other solutes ph of 6.8 to 7.0 Solutes in saliva Salivary amylase- an enzyme that begins starch digestion Lingual lipase- activated by stomach acid and digest fat after the food is swallowed Mucus- binds and lubricates the food mass and aids in swallowing Lysozyme- kills bacteria 9

10 Mastication(Chewing) Mastication is a repetitive sequence of jaw opening and closing with a profile in the vertical plane called the chewing cycle. Mastication consists of a number of chewing cycles. The human chewing cycle consists of three phases: 1. Opening phase: the mouth is opened and the mandible is depressed 2. Closing phase: the mandible is raised towards the maxilla 3. Occlusal or intercuspal phase: the mandible is stationary and the teeth from both upper and lower arches approximate 10

11 Deglutition (swallowing) Sequence Voluntary stage Push food to back of mouth Pharyngeal stage Raise Soft palate Larynx Tongue to soft palate Esophageal stage Contract pharyngeal muscles Open esophagus Start peristalsis 11

12 Phases of Deglutition Coordinated by swallowing center in the medulla oblongata and pons Buccal phase The voluntary stage in which the tongue collects food, presses it against the plate to form a bolus, and pushes it back into the oropharynx Pharyngeal-esophageal phase Three actions block food and drink from reentering the mouth or entering the nasal cavity or larynx The root of the tongue blocks the oral cavity The soft palate rises and blocks the nasopharynx The muscles pull the larynx up against the epiglottis to close the airway that leads to the trachea Esophageal Stage- Food is moved through the esophagus by peristalsis (the wave like muscle contractions of the inner circular and outer longitudinal muscles). At the end of the pharyngeal stage of the swallow, it must relax to allow the bolus to enter the esophagus. 12

13 Structure of GI tract

14 Structure of GI tract Mucosa The inner layer of the tract that is a mucous membrane that is composed of a layer of epithelium- simple columnar in most of the GI tract a thin layer of smooth muscle ( is responsible for the mucosal folds, or rugae, that serves to increase the surface area for digestion.) Is the most highly differentiated layer of the GI tract. Submucosa binds the mucosa to the underlying muscle layer. blood vessels, lymphatics, a nerves plexus, glands that secrete lubricating mucus into the lumen A thick layer of muscle that under lies the submucosa begins at the mouth where it is composed of a mixture of smooth and striated muscle (for voluntary swallowing) and the external sphincter where it is skeletal. At the distal pharynx it turns into all smooth muscle that courses throughout the rest of the tract. The involuntary smooth muscle consist of an inner circular and an outer longitudinal layer. 14

15 Structure of GI tract..ctd Serosa The outermost layer of the GI tract. Composed of a thin layer of r tissue topped by a serous membrane (mesothelium) Begins in the lower 3 to 4 cm of the esophagus and ends with the sigmoid colon When the outer fibrous layer is attached to surrounding tissue it is called adventitia See this at the oral cavity, pharynx, most of the esophagus, and the rectum It secretes fluid that allows the tract structures to glide over each other without friction. It is also referred to as visceral peritoneum. 15

16 Peristalsis and Segmentation 16

17 Law of Gut Peristaltic Movement + Movement towards gravity(mouth to anus) 17

18 Esophagus Usually collapsed (closed) Functions Secrete mucous Transport food Sphincters Upper Lower 18

19 Esophagus..ctd Esophagus A straight muscular tube about cm long It begins at the level of the cricoid cartilage, inferior to the larnyx behind the trache a and extends through the chest cavity, pierces the diaphragm at the esophageal hiatus, and meets with the stomach at an opening called the cardiac orifice. It transports food to the stomach and secretes mucus, which aids transport. The inferior segment is constricted forming the lower esophageal sphincter which, along with the diaphragm, closes to prevent back flow of stomach contents Heartburn- when HCl from the stomach regurgitates back into the lower esophagus resulting in a burning sensation. 19

20 Stomach Usually J shaped Left side, anterior to the spleen Mucous membrane G cells make gastrin Goblet cells make mucous Gastric pit Oxyntic gland Parietal cells Make HCl Chief cells Zymogenic cells Pepsin Gastric lipase 20

21 Anatomy of the Stomach 21

22 Stomach 3 muscle layers Oblique Circular Longitudinal Regions Cardiac sphincter Fundus Antrum (pylorus) Pyloric sphincter Vascular Inner surface thrown into folds Rugae Contains enzymes that work best at ph

23 Stomach Functions Mix food Reservoir Start digestion of Protein Nucleic acids Fats Activates some enzymes Destroy some bacteria Makes intrinsic factor B 12 absorption Destroys some bacteria Absorbs Alcohol Water Lipophilic acid B 12 23

24 Stomach-Phases

25 HCl Generation

26 Small Intestine Extends from pyloric sphincter ileocecal valve Regions Duodenum Jejenum Ileum Movements Segmentation Peristalsis 26

27 Small Intestine Absorbs 80% ingested water Electrolytes Vitamins Minerals Carbonates Active/facilitated transport Monosaccharides Proteins Di-/tripeptides Amino acids Lipids Monoglycerides Fatty acids Micelles Chylomicrons 27

28 Small Intestine-structure

29 Structure of the Villi in the Small Intestine 29

30 Small Intestine Secretes digestive enzymes Peptidases Amino- Di- Tri- Sucrases Maltase Lactase Saccharidases Di- Tri- Lipase Nucleases 30

31 Small Intestine Control Requires pancreatic enzymes & bile to complete digestion 31

32 Absorption at intestine

33 Large Intestine Extends from ileocecal valve to anus Regions Cecum Appendix Colon Ascending Transverse Descending Rectum Anal canal 33

34 Anatomy of the Large Intestine 34

35 Large Intestine Histology No villi No permanent circular folds Smooth muscle Taeniae coli Haustra Epiploic appendages Otherwise like rest of Gl tract 35

36 Large Intestine Functions Mechanical digestion Haustral churning Peristalsis Reflexes Gastroileal Gastrocolic Chemical digestion Bacterial digestion Ferment carbohydrates Protein/amino acid breakdown Absorbs More water Vitamins B K Concentrate/eliminate wastes 36

37 Feces Formation and Defecation Chyme dehydrated to form feces Feces composition Water Inorganic salts Epithelial cells Bacteria Byproducts of digestion Defecation Peristalsis pushes feces into rectum Rectal walls stretch Control Parasympathetic Voluntary 37

38 Defecation

39 Summary-Digestion and absorption 39

40 Excretory System

41

42 The Kidney

43 Nephron

44 Countercurrent Multiplication and Concentration of Urine Figure 26.13b

45 Glomerulus

46 Glomerular Filtrate

47 Ureters and Urinary Bladder

48 Urinary Bladder

49 Composition of Urine

50 Urinary bladder structure

51 Innervations of urinary bladder

52 Micturition

53 Skin and sweat glands

54 Functions Skin performs the following functions: Protection Sensation Heat regulation Control of evaporation Storage and synthesis Absorption Water resistance

55 Perspiration Perspiration (sweating, transpiration or diaphoresis) is the production of a fluid consisting primarily of water as well as various dissolved solids (chiefly chlorides), that is excreted by the sweat glans in the skin of mammals

56 Liver

57 Internal structure-liver

58 Functions-Liver

59 Liver cells

60 Intestinal juices daily secretions

61 Bile secretion

62 Composition of Bile

63 Enterohepatic circulation

64 Gall bladder-function