Digestive System

Home , Gastric glands, Gastric pits

Business  Reminder: No class Monday (Memorial Day)  Midterm 2 is Tuesday 5/28/13  Optional review session tomorrow @ 5pm  Homework due in Lab 1. PreLab 8 (1pt) 2. Replace a Missing Assignment (4 pts)  Homework page 17 Digestive System

Part 1 Introduction  Every cell requires a constant energy source  Ingested food is complex  Modification is needed to utilize Introduction  Digestive system is a tube  Gastrointestinal tract  Specialized regions  Mouth  Pharynx  Esophagus  Stomach  Small intestine  Large intestine Parotid gland Mouth (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland

Esophagus Pharynx Stomach Pancreas Liver (Spleen) Gallbladder Transverse colon Duodenum Descending colon Small Jejunum Ascending colon intestine Ileum Cecum Large Sigmoid colon intestine Rectum Vermiform appendix Anus Anal canal

Copyright © 2010 Pearson Education, Inc. Figure 23.1 Introduction  Digestive processes 1. Ingestion 2. Propulsion 3. Mechanical digestion 4. Chemical digestion 5. Absorption 6. Defecation Ingestion Food Mechanical digestion Pharynx • Chewing (mouth) Esophagus • Churning (stomach) Propulsion • Segmentation • Swallowing (small intestine) (oropharynx) Chemical • Peristalsis

digestion Stomach (esophagus, stomach, small intestine, large intestine) Absorption Lymph vessel

Small intestine Large Blood intestine vessel Mainly H2O Feces

Defecation Anus

Copyright © 2010 Pearson Education, Inc. Figure 23.2 Introduction  Histology of the alimentary canal  Four basic layers (tunics)  Tunica mucosa  Protection and absorption Epithelium and connective tissue  Tunica submucosa  Connective tissue  Tunica muscularis (externa)  Double layer of muscle  Tunica serosa  Visceral peritoneum  Single layer of epithelium Introduction  Peritoneum  Parietal peritoneum  Mesentery  Visceral peritoneum  Omentum

Intrinsic nerve plexuses • Myenteric nerve plexus • Submucosal nerve plexus Glands in submucosa Mucosa • Epithelium • Lamina propria • Muscularis mucosae Submucosa Muscularis externa • Longitudinal muscle • Circular muscle

Nerve Serosa Artery • Epithelium Vein • Connective tissue Gland in mucosa Lumen Lymphatic Duct of gland outside Mucosa-associated Mesentery vessel alimentary canal lymphoid tissue

Dorsal mesentery

Parietal peritoneum Ventral mesentery Visceral peritoneum Peritoneal Alimentary Liver cavity canal organ (a) Schematic cross sections of abdominal cavity illustrate the peritoneums and mesenteries.

Liver

Gallbladder Lesser omentum

Stomach Duodenum

Transverse colon

Small intestine

Cecum

Urinary bladder (b)

 Mouth  Cheek, palate, tongue  Opens into oropharynx  Salivary glands Soft palate Palatoglossal arch Uvula Hard palate

Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx

Esophagus

Trachea (a) Sagittal section of the oral cavity and pharynx

Figure 23.7a Salivary glands secrete about 1250 ml of saliva per day!

Tongue Teeth Parotid Ducts of gland sublingual gland Parotid duct Masseter muscle Frenulum of tongue Body of Sublingual mandible (cut) gland Posterior belly Mylohyoid of digastric muscle (cut) muscle Submandibular Anterior belly of Submandibular duct digastric muscle gland Mucous Serous cells (a) cells forming demilunes (b)

Copyright © 2010 Pearson Education, Inc. Figure 23.9 Digestive System  Teeth  Held in place by periodontal ligaments  Gingiva covers bone  2 dentitions  Deciduous  Permanent Teeth 20 deciduous 32 permanent

Incisors Incisors Central (6–8 mo) Central (7 yr) Lateral (8 yr) Lateral (8–10 mo) Canine (eyetooth) Canine (eyetooth) (11 yr) (16–20 mo) Premolars Molars (bicuspids) First molar First premolar (10–15 mo) Deciduous (11 yr) Second molar (milk) teeth Second premolar (about 2 yr) (12–13 yr) Molars First molar (6–7 yr) Second molar (12–13 yr) Third molar Permanent (wisdom tooth) teeth (a) (17–25 yr)

Copyright © 2010 Pearson Education, Inc. Figure 23.10a Digestive System  Teeth  Anatomy  Crown covered by enamel  Pulp cavity  Dentin  Roots  Function  Break down food  Mixed with saliva to form bolus Enamel Dentin Crown Dentinal tubules Pulp cavity (contains blood vessels and Neck nerves) Gingiva (gum)

Cementum

Root canal

Root Periodontal ligament

Apical foramen

Bone

Copyright © 2010 Pearson Education, Inc. Figure 23.11 Digestive System  Esophagus  Pharynx to stomach  Moves bolus to stomach  Peristalsis  Cardiac (gastroesophageal) sphincter  Heartburn  Histology  Mucosa  Stratified squamous epithelium  Abundant mucous glands  Serosa  Connective tissue Parotid gland Mouth (oral cavity) Sublingual gland Salivary Tongue Submandibular glands gland

Figure 23.1 Relaxed muscles 4 Food is moved through Circular muscles the esophagus to the contract stomach by peristalsis. Bolus of food

Longitudinal muscles contract

Gastroesophageal sphincter closed

Stomach

Figure 23.13, step 4 Relaxed 5 The gastroesophageal muscles sphincter opens, and food enters the stomach.

Gastroesophageal sphincter opens

Figure 23.13, step 5 Mucosa (contains a stratified squamous epithelium)

Submucosa (areolar connective tissue)

Lumen Muscularis externa • Longitudinal layer • Circular layer Adventitia (fibrous connective tissue) (a)

Figure 23.12a simple columnar epithelium

Mucosa (contains a stratified squamous epithelium)

Esophagus stomach junction

(b)

Copyright © 2010 Pearson Education, Inc. Figure 23.12b Cardia Fundus Esophagus Muscularis externa Serosa • Longitudinal layer • Circular layer Body • Oblique layer Lesser Lumen curvature Rugae of mucosa

Greater curvature Pyloric Pyloric Duodenum canal antrum Pyloric sphincter (a) (valve) at pylorus

Figure 23.14a Digestive System  Stomach  From cardiac orifice to pyloric sphincter  Rugae  Greater curvature  Convex lateral surface  Greater omentum  Lesser curvature  Concave medial surface  Lesser omentum Falciform ligament Liver Gallbladder

Spleen Stomach

Ligamentum teres

Greater omentum

Small intestine

Cecum

(a)

Figure 23.30a Liver

Gallbladder Lesser omentum

Stomach Duodenum

Transverse colon

Small intestine

Cecum

Urinary bladder (b)

Figure 23.30b Digestive System  Stomach  Four tunics  Muscularis  Additional layer of muscle in an oblique orientation  Three layers of smooth muscle Cardia Fundus Esophagus Muscularis externa Serosa • Longitudinal layer • Circular layer Body • Oblique layer Lesser Lumen curvature Rugae of mucosa

Greater curvature Pyloric Pyloric Duodenum canal antrum Pyloric sphincter (a) (valve) at pylorus

Figure 23.14a Digestive System  Stomach  Four tunics  Mucosa  Gastric glands o Mucous cells = Mucous o Parietal cells = Intrinsic factor and HCL o Zymogenic (chief) cells = Pepsinogen o Enteroendocrine cells = Gastrin and cholecystokinin Surface epithelium

Mucosa

Mucosa contains gastric glands Lamina propria Muscularis mucosae Submucosa (contains submucosal plexus) Oblique layer Muscularis externa Circular layer (contains myenteric Longitudinal plexus) layer

Serosa Stomach wall (a) Layers of the stomach wall (l.s.)

Figure 23.15a Gastric pits

Surface epithelium (mucous cells)

Gastric pit Mucous neck cells Parietal cell Chief cell Gastric gland

Enteroendocrine cell (b) Enlarged view of gastric pits and gastric glands

Figure 23.15b Pepsinogen Pepsin HCl

Mitochondria Parietal cell

Chief (Zymogenic) cell

Enteroendocrine cell (c) Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland

Figure 23.15c Digestive System  Chemical digestion in the stomach  Protein catabolism → polypeptides  Secretions HCl  Pepsinogen → pepsin  HCl  pH 1.5–3.5  Denatures protein in food  Kills many bacteria  Intrinsic factor

 Required for absorption of vitamin B12 in small intestine Pepsinogen Pepsin HCl

Mitochondria Parietal cell

Chief (Zymogenic) cell

Enteroendocrine cell (c) Location of the HCl-producing parietal cells and pepsin-secreting chief cells in a gastric gland

Figure 23.15c Digestive System  Chemical digestion in the stomach  Enteroendocrine cells  Secrete hormone like substances  Gastrin  Cholecystokinin o Actually produced by enteroendocrine cells in the duodenum

Digestive System  Chemical digestion in the stomach  Chyme  Product of stomach digestion  Prevention of autodigestion  Mucous  Gastritis  Peptic ulcers  Gastric ulcers  Duodenal ulcers Bacteria

Mucosa layer of stomach

(a) A gastric ulcer lesion (b) H. pylori bacteria

Figure 23.16 Digestive System  Control of gastric secretions  Neural control  Vagus nerve  Enteric nervous system  Hormonal control  Gastrin

Digestive System  Control of gastric secretions  Stimulatory and inhibitory events occur in three phases 1. Cephalic 2. Gastric 3. Intestinal

Stimulatory events Inhibitory events

Cephalic 1 Sight and thought Cerebral cortex Lack of Cerebral 1 Loss of phase of food Conditioned reflex stimulatory cortex appetite, impulses to depression 2 Stimulation of Hypothalamus Vagus parasym- taste and smell and medulla nerve pathetic receptors oblongata center

1 Stomach Vagovagal Medulla Vagus Gastrin G cells 1 Excessive distension reflexes nerve secretion acidity activates declines (pH <2) stretch in stomach Gastric receptors Local Overrides Sympathetic 2 Emotional phase reflexes parasym- nervous upset pathetic system controls activation 2 Food chemicals G cells Gastrin (especially peptides and release caffeine) and rising pH to blood activate chemoreceptors Stomach secretory activity Entero- Local 1 Distension gastric reflexes of duodenum; presence of 1 Presence of low Intestinal reflex fatty, acidic, pH, partially digested (enteric) Vagal hypertonic foods, fats, or gastrin nuclei chyme, and/or hypertonic solution release Brief Intestinal in medulla irritants in in duodenum when to blood effect phase stomach begins to Pyloric the duodenum empty sphincter

Release of intestinal 2 Distension; hormones (secretin, presence of cholecystokinin, vasoactive fatty, acidic, intestinal peptide) partially digested food Stimulate in the Inhibit duodenum

Figure 23.17 Enteric Nervous System  “In house nerve supply” to alimentary canal  Local reflex arcs  Regulate digestive system activity  Digestive activity also subject to extrinsic controls through ANS Digestive System  Control of gastric secretions  Stimulatory and inhibitory events occur in three phases 1. Cephalic  Hearing, seeing, smelling, tasting, thinking about food  Vagus nerve stimulated o Gastric secretion starts

Digestive System  Control of gastric secretions  Stimulatory and inhibitory events occur in three phases 1. Cephalic 2. Gastric  Arrival of food in stomach  Stomach distension, peptides, low acidity → gastrin released o Relaxes pyloric sphincter o Increases stomach motility

Digestive System  Control of gastric secretions  Stimulatory and inhibitory events occur in three phases 1. Cephalic 2. Gastric 3. Intestinal  Chyme reaches duodenum  Intestinal distention → enterogastric reflex  Release of secretin, CCK, VIP o Inhibit stomach motility and delay emptying

Stimulatory events Inhibitory events

Release of intestinal 2 Distension; hormones (secretin, presence of cholecystokinin, vasoactive fatty, acidic, intestinal peptide) partially digested food Stimulate in the Inhibit duodenum

Figure 23.17 Pyloric Pyloric Pyloric valve valve valve closed closed slightly opened

1 Propulsion: Peristaltic 2 Grinding: The most 3 Retropulsion: The pyloric waves move from the vigorous peristalsis and end of the stomach acts as a fundus toward the mixing action occur pump that delivers small pylorus. close to the pylorus. amounts of chyme into the duodenum, simultaneously forcing most of its contained material backward into the stomach.

Figure 23.19 Presence of fatty, hypertonic, acidic chyme in duodenum

Duodenal entero- Chemoreceptors and endocrine cells stretch receptors

Secrete Target

Enterogastric Reflex Enterogastrones Via short Via long (secretin, reflexes reflexes cholecystokinin, vasoactive intestinal peptide) Enteric CNS centers neurons sympathetic Duodenal activity; stimuli parasympathetic decline activity

Contractile force and Initial stimulus rate of stomach Physiological response emptying decline Stimulate Result Inhibit

Figure 23.20