Digestive System CHAPTER 14

Size: px

Start display at page:

Download "Digestive System CHAPTER 14"

Dorcas Griffith
6 years ago
Views:

1 Digestive System CHAPTER 14

3 Digestive System b_ehap_8/activities/chapter14/act14a.ht ml

4 Functions of Digestion Ingestion - intake of food Propulsion a. Peristalsis - alternating contracting & relaxation b. Segmentation - movement of food back & forth across an organ mixing with digestive juices

5 Mechanical Digestion - breaking food into smaller fragments mouth & stomach mastication- chewing Chemical Digestion - breakdown large molecules into their building blocks; occurs in mouth, stomach & small intestine

6 Polysaccharides Starch composed of monosaccharides (glucose) Lipids Fatty Acids & Glycerol Proteins Amino Acid Chains Nucleic Acids Nucleotide chains

7 Absorption - transport of nutrients into the blood Defecation - elimination of waste in a solid form (feces)

8 Divisions of Digestive System Alimentary Canal or Gastrointestinal Tract (GI) coiled hollow tube with 2 openings mouth, pharynx, esophagus, stomach, small intestine, large intestine

9 Accessory Organs - assist in breakdown of molecules teeth, tongue, salivary glands, pancreas, liver, gall bladder

10 Organs of the Alimentary Canal 1. Mouth or oral cavity lips (labia) - protect oral cavity opening cheeks - forms lateral walls hard palate - forms anterior roof soft palate - forms posterior roof uvula - fleshy fingerlike projection; closes nasal cavity when swallowing vestibule - area between lips & cheeks and teeth & gums

12 2. Pharynx - common throat oropharynx - posterior to oral cavity nasopharynx - part of respiratory passageway laryngopharynx - continues to esophagus; larynx - voice box

13 3. Esophagus - gullet; runs from pharynx through the diaphragm to the stomach 25 cm long smooth muscle propels food to stomach through peristalsis lkral/peristalsis/

14 4. Stomach A. Structure Cardiac surrounds junction between esophagus & stomach Fundus superior portion Body main portion; lined with folded walls called rugae that disappear when stomach is full Pylorus terminal portion

17 B. Valves or sphincters Cardioesophageal (cardiac) leads food into stomach Pyloric leads partial digested food (chyme) into small intestine C. Curvatures: Greater outer (lateral) curve Lesser inner (medial) curve

19 C. Mechanical Digestion 3 muscle layers segmentation of food 1 st longitudinal 2 nd circular 3 rd oblique

20 p. 416 Fig 14.4 D. Chemical digestion Walls lined with gastric pits that lead to the gastric gland Gastric gland contains 3 types of cells 1. Mucus neck cells secrete alkaline sticky mucus to protect stomach walls 2. Parietal cells produces HCl which activates enzyme production 3. Chief cells produce protein digestive enzymes called pepsinogen (inactive form of pepsin)

22 Sequence of events: 1. food enters stomach 2. Parietal cells secrete HCl which lowers ph 3. low ph triggers chief cells to produce pepsinogen 4. pepsinogen converted to its active form of pepsin

23 5. Small Intestine A. Structure Extends from the pyloric sphincter to the ileocecal valve 7 m long Mesentary web like membrane that coils small intestine & holds it intact

24 3 subdivisions: Duodenum curves around the pancreas; receives chyme from stomach, enzymes from pancreas & bile from liver Jejunum middle portion; bulk of digestion & absorption Ileum terminal portion

26 B. Chemical Digestion 1. pyloric sphincter controls amount of food entering from stomach 2. pancreas produces enzymes that are secreted to small intestines through pancreatic duct 3. Bile formed in liver is secreted through bile duct 4. Pancreatic & bile ducts join to form hepatopancreatic ampulla 5. together enzymes,bile and bicarbonate (neutralize acids) enter duodenum through duodenal papilla

27 C. Absorption Peyer s Patches collection of lymphatic tissue that increases toward end of small intestine that prevents absorption of bacteria

28 Surface area increased by 3 structures: Circular folds (plicae circularis) deep folds of inner walls

29 Villi fingerlike projections that contain bv & lymphatic duct called the lacteal Microvilli brush border ; projections of the cell membrane that give a fuzzy appearance

30 Chemical Influences Carbohydrates sugars & starches Salivary amylase mouth Pancreatic amylase produced by pancreas & sent to duodeum Brush border enzymes dextrinase, glucoamylase Lactase (lactose), maltase (maltose), sucrase (sucrose) Produced & act in small intestine

31 Proteins Begins in stomach with pepsin & rennin (more abundant in children) Pancreas trypsin, chymotrypsin, carboxypeptidase Brush border aminopeptidase, carboxypeptidase & dipeptidase

32 Fats Bile emulsifies fats Pancreatic lipases sent to small intestine to complete fat digestion

33 Nucleic Acids Pancreas produces nucleases to breakdown nucleic acids (DNA, RNA)

34 HORMONE SOURCE STIMULUS ACTION GASTRIN Stomach Food in stomach release of gastric juice Mobility of small intestine Relaxes ileocecal valve HISTAMINE Stomach Food in stomach activates parietal cells SOMATOSTATIN stomach Food in stomach Inhibits secretion of gastric & pancreatic juices Inhibits emptying of stomach & gall bladder SECRETIN duodenum Chyme from stomach Release of pancreatic juices & bile CHOLECYSTOKININ (CCK) Duodenum Chyme from stomach Release of pancreatic juices & bile Relaxes duodenal papillae GASTRIC INHIBITORY PEPTIDE (GIP) Duodenum Chyme from stomach inhibits secretion of gastric juices

35 6. Large Intestine Extends from ileocecal valve to anus Absorption of water & elimination of waste No villi Lined with goblet cells that produce mucus for lubrication Outer walls puckered with haustra which aids in contraction

36 Cecum 1 st portion ; ileocecal valve that allows indigestible material from sm. Intestine Appendix sac extending from cecum

37 Ascending colon travels up right side of abdominal cavity ; turns at the hepatic flexure Transverse colon travels across the abdomin; turns at the splenic flexture

38 Descending colon travels down left side of abdomen Sigmoid colon S shaped Rectum storage chamber Anal sphincter external & internal; voluntary & involuntary muscles; opens during defecation

39 ACCESSORY ORGANS PANCREAS Gland that extends across abdomen from spleen to duodenum Located retroperitoneal behind parietal peritoneum Functions: produces enzymes in a alkaline fluid Produces insulin ( breaks down glucose) and glucagon hormone that raises glucose level)

40 PANCREAS

41 LIVER Largest gland ; 4 lobes Suspended from diaphragm by falciform ligament Produces bile yellow/green water solution containing bile salts, bile pigments (bilirubin), cholesterol, phospholipids and electrolytes Bile emulsifies fat into small globules Right & left hepatic ducts collect bile Fuse into the common hepatic duct

43 GALL BLADDER Green sac within lobes of liver When not digesting food bile backs up into the cystic duct & is stored in gall bladder Bile becomes concentrated in gall bladder due to water absorption

44 Gallstones results from too much water absorption and cholesterol crystallizes Jaundice results from blockage of common hepatic or bile ducts, hepatitis (inflammation of liver) or cirrhosis (hardening of liver)

47 SALIVARY GLANDS Parotid lies anterior to ears; largest Submandibular below jaw Sublingual beneath tongue Empty secretions in floor of mouth Saliva mixture of mucus (moistens & binds food into bolus), amylase (digest starch) and antibodies (inhibit bacteria)

49 TEETH Massication of food Deciduous teeth 1 st set; 20 Permanent teeth 2 nd set; 32

50 Incisors front; chisel shaped for cutting Canines corner fangs; puncture & pierce Premolars / bicuspids sides; grinding Molars rear; crush & grind

51 Crown exposed area; above gum Root beneath the gum Neck connect root to crown Gingiva gums

52 Enamel hard outer covering of crown Dentin bone like material under enamel; composes bulk of tooth Cementum glue like substance on outer root surface

53 Pulp cavity contains pulp blood vessels, nerves & connective tissue provides nutrients to tooth & sensations Root canal extension of pulp into root Peridontal ligament holds tooth in socket

Two main groups Alimentary canal continuous coiled hollow tube Accessory digestive organs

Digestion Breakdown of ingested food Absorption of nutrients into the blood Metabolism Production of cellular energy (ATP) Constructive and degradative cellular activities Two main groups Alimentary canal