Chapter 26 Digestive System Part 1 Overview, Mouth, Esophagus

Functions of the digestive system Ingestion Digestion = breakdown of food into small structures and molecules Mechanical digestion = physical breakdown by teeth, tongue, muscles Chemical digestion = breakdown using enzymes Propulsion Secretion = production and release of mucin and fluids to aid digestion Absorption = movement of electrolytes, fats, proteins, vitamins, water across GI tract into blood and lymph vessels Elimination = get rid of waste

Gastrointestinal Tract Categories: Digestive organs Gastrointestinal Tract (Digestive Organs) Oral cavity Make up gastrointestinal (GI) tract (AKA digestive tract or alimentary canal) oral cavity pharynx esophagus stomach small intestine large intestine anus Pharynx Esophagus Stomach Large intestine Small intestine Anus

Accessory Digestive Organs Fig. 26.1 Categories: Accessory digestive organs Accessory Digestive Organs Parotid salivary gland Teeth Tongue Not part of GI tube Develop as outgrowths; connected to GI tube Assist in digestion salivary glands teeth and tongue liver gallbladder pancreas Sublingual salivary gland Submandibular salivary gland Liver Gallbladder Pancreas

Movement within GI tract Fig. 26.2 Relaxation Bolus Lumen Wall of GI tract (a) Peristalsis Wave of contraction Movement within GI tract Peristalsis = rhythmic formation of ripples along tube moves material forward like squeezing a toothpaste tube from the bottom

Movement within GI tract Mixing Further mixing (b) Segmentation Movement within GI tract Segmentation = rhythmic churning and mixing of material squeezes at multiple locations simultaneously moves material back and forth, mixing and breaking into smaller pieces

Oral Cavity First site of mechanical and chemical digestion Fig. 26.3 Superior lip Oral Cavity Superior labial frenulum Transverse palatine folds First site of mechanical and chemical digestion Vestibule = space between cheeks or lips and gums Oral cavity proper = teeth and area within Hard palate Soft palate Palatoglossal arch Uvula Palatopharyngeal arch Fauces Palatine tonsil Tongue Salivary duct orifices Lingual frenulum Sublingual Submandibular Teeth Inferior labial frenulum Gingivae Inferior lip

Fig. 26.3 Oral cavity Tongue Vestibule (b) Sagittal section

Oral Cavity: lips Cheeks end at lips Fig. 26.3 (a) Oral cavity, anterior view Superior lip Cheeks end at lips primarily formed from orbicularis oris covered with keratinized stratified squamous epithelium reddish hue from abundant blood vessels Inferior lip

Oral Cavity: gums Gums = gingivae Fig. 26.3 (a) Oral cavity, anterior view Superior lip Superior labial frenulum Gums = gingivae dense irregular connective tissue, with layer of nonkeratinized stratified squamous epithelium Labial frenulum attaches internal surfaces of lips to gingivae Inferior labial frenulum Gingivae Inferior lip

Oral Cavity: palate Roof of oral cavity, separates from nasal cavity Fig. 26.3 (a) Oral cavity, anterior view Transverse palatine folds Roof of oral cavity, separates from nasal cavity Hard palate = anterior 2/3 formed from maxillae and palatine bones has transverse palatine folds that help manipulate food Soft palate = posterior 1/3 skeletal muscle covered with nonkeratinized stratified squamous epithelium uvula and soft palate elevate during swallow to block nasal cavity Hard palate Soft palate Uvula

Oral Cavity: tongue Primarily skeletal muscle Fig. 26.3 (a) Oral cavity, anterior view Lingual frenulum Tongue Primarily skeletal muscle covered with stratified squamous epithelium has papillae to add texture and surface area Attached to floor of oral cavity by lingual frenulum Helps make sounds Manipulates and mixes food during chewing

Fig. 26.3 Oral Cavity: tongue Oral cavity Tongue Vestibule Lingual tonsil Oropharynx Uvula Helps form chewed food into bolus, soft moist ball of food and saliva Pushes bolus to oropharynx for swallowing Lingual tonsils sit on posteroinferior tongue surface

Oral Cavity: salivary glands Fig. 26.3 (a) Oral cavity, anterior view Submandibular Sublingual Salivary duct orifices Produce and secrete saliva 1.0 to 1.5 L per day, mostly during meals 99.5% water + small amount of amylase (breaks down starch) contains antibodies and antibacterials moistens food cleans and lubricates oral cavity dissolves food particles for tastebuds

Oral cavity: salivary glands Fig. 26.4 Oral cavity: salivary glands Parotid salivary gland Parotid duct A few unicellular intrinsic salivary glands within mouth secrete lingual lipase, activated by acidic stomach to break down lipids Most saliva produced by multicellular salivary glands Masseter muscle Mucosa (cut) Sublingual ducts Submandibular duct Sublingual salivary gland Submandibular salivary gland Mylohyoid muscle (cut) (a) Salivary glands

Oral cavity: salivary glands Fig. 26.4 Oral cavity: salivary glands Parotid salivary gland Parotid duct Parotid salivary glands anterior to ear partly overlays masseter muscle produces 25-30% of saliva connects to mouth through parotid duct Masseter muscle Mucosa (cut) Sublingual ducts Submandibular duct Sublingual salivary gland Submandibular salivary gland Mylohyoid muscle (cut) (a) Salivary glands

Oral cavity: salivary glands Fig. 26.4 Oral cavity: salivary glands Parotid salivary gland Parotid duct Submandibular salivary glands inferior to mandible produce 60-70% of saliva connect to mouth through submandibular duct Masseter muscle Mucosa (cut) Sublingual ducts Submandibular duct Sublingual salivary gland Submandibular salivary gland Mylohyoid muscle (cut) (a) Salivary glands

Oral cavity: salivary glands Fig. 26.4 Oral cavity: salivary glands Parotid salivary gland Parotid duct Sublingual salivary glands inferior to tongue produces 3-5% of saliva Masseter muscle Mucosa (cut) Sublingual ducts Submandibular duct Sublingual salivary gland Submandibular salivary gland Mylohyoid muscle (cut) (a) Salivary glands

Oral cavity: teeth Collectively called dentition crown is exposed part Fig. 26.5 Crown Enamel Collectively called dentition crown is exposed part neck is smaller, just within gums root anchors tooth to bone with periodontal ligaments fits in dental alveoli on mandible and maxillae Gingiva Neck Dentin Pulp cavity Root canal Root Cementum Periodontal ligaments Dental alveolus Blood vessels and nerves in apical foramen

Oral cavity: teeth Layers of tooth enamel forms crown Fig. 26.5 Crown Enamel Layers of tooth enamel forms crown hardest substance in body formed of calcium phosphate cementum is hardened layer around root dentin forms most of mass of tooth harder than bone pulp cavity is center of tooth and root Gingiva Neck Dentin Pulp cavity Root canal Root Cementum Periodontal ligaments Dental alveolus Blood vessels and nerves in apical foramen

Oral cavity: teeth Layers of tooth Fig. 26.5 Crown Enamel Layers of tooth Root canal opens into connective tissue through apical foramen blood vessels and nerves pass through Gingiva Neck Dentin Pulp cavity Root canal Root Cementum Periodontal ligaments Dental alveolus Blood vessels and nerves in apical foramen

Baby teeth are deciduous teeth Start to erupt at about 6 months Fig. 26.6 Central incisor (7–9 mos.) Lateral incisor (9–11 mos.) Canine (18–20 mos.) 1st molar (14–16 mos.) 2nd molar (24–30 mos.) Upper teeth 2nd molar (20–22 mos.) Lower teeth 1st molar (12–14 mos.) Canine (16–18 mos.) Baby teeth are deciduous teeth Start to erupt at about 6 months incisors first Permanent teeth eventually replace them Wisdom teeth are 3rd molars; erupt in teens or 20s Lateral incisor (7–9 mos.) Central incisor (6–8 mos.) (b) Deciduous teeth

Front teeth (4) are incisors Fig. 26.6 Right Upper (Maxillary) Quadrant Left Upper (Maxillary) Quadrant Central incisor (7–8 yrs.) Front teeth (4) are incisors Canines (AKA cuspids) are sharp for puncturing and tearing Premolars (AKA bicuspids) are used to crush and grind Molars are thickest, for grinding and crushing have 3+ roots Lateral incisor (8–9 yrs.) Canine (11–12 yrs.) 1st premolar (10–11 yrs.) 2nd premolar (10–12 yrs.) Upper teeth 1st molar (6–7 yrs.) 2nd molar (12–13 yrs.) 3rd molar (17–25 yrs.) Hard palate 3rd molar (17–25 yrs.) 2nd molar (11–13 yrs.) 1st molar (6–7 yrs.) Lower teeth 2nd premolar (11–12 yrs.) 1st premolar (10–12 yrs.) Canine (9–10 yrs.) Lateral incisor (7–8 yrs.) Central incisor (6–7 yrs.) Right Lower (Mandibular) Quadrant Left Lower (Mandibular) Quadrant (c) Permanent teeth

Serous membranes Parietal peritoneum lines inside surface of body wall Fig. 26.7 Serous membranes Liver Diaphragm Stomach Lesser omentum Pancreas Parietal peritoneum lines inside surface of body wall Visceral peritoneum covers surface of internal organs Peritoneal cavity is between layers of membrane Duodenum Mesocolon Transverse colon Jejunum Greater omentum Parietal peritoneum Mesentery proper Visceral peritoneum Ileum Peritoneal cavity Rectum Urinary bladder

Fig. 26.7 Serous membranes Liver Diaphragm Mesenteries are folds of peritoneum around intraperitoneal GI tract organs Greater omentum extends from greater curvature of stomach often accumulates adipose Lesser omentum connects lesser curvature of stomach and proximal duodenum to liver Stomach Lesser omentum Pancreas Duodenum Mesocolon Transverse colon Jejunum Greater omentum Parietal peritoneum Mesentery proper Visceral peritoneum Ileum Peritoneal cavity Rectum Urinary bladder

Serous membranes Mesentery proper suspends small intestine Fig. 26.7 Serous membranes Liver Diaphragm Stomach Lesser omentum Mesentery proper suspends small intestine full of blood vessels, lymph vessels, and nerves Mesocolon is fold of peritoneum that attaches parts of large intestine to posterior abdominal wall Pancreas Duodenum Mesocolon Transverse colon Jejunum Greater omentum Parietal peritoneum Mesentery proper Visceral peritoneum Ileum Peritoneal cavity Rectum Urinary bladder

4 layers of tissues in GI tract Mucosa Fig. 26.9 Epithelium 4 layers of tissues in GI tract variations from one organ to another Lamina propria Muscularis mucosae Mesentery Vein Artery Submucosa Lymph vessel Submucosal gland Lumen Blood vessel Submucosal nerve plexus Muscularis Inner circular layer Myenteric nerve plexus Outer longitudinal layer Serosa

Mucosa epithelium lining lumen Fig. 26.9 Mucosa Epithelium Lamina propria Muscularis mucosae Mesentery Mucosa epithelium lining lumen lamina propria is areolar connective tissue muscularis mucosae Vein Artery Lymph vessel Lumen

Submucosa areolar or dense irregular connective tissue Fig. 26.9 Submucosa areolar or dense irregular connective tissue includes mucin-secreting glands (ducts project through mucosa) includes blood and lymph vessels, nerves Mesentery Vein Artery Submucosa Lymph vessel Submucosal gland Lumen Blood vessel Submucosal nerve plexus

Muscularis 2 layers of smooth muscle inner layer lies circumferentially; thickening makes a sphincter outer layer lies longitudinally Myenteric nerve plexus controls contractions Lumen Muscularis Inner circular layer Myenteric nerve plexus Outer longitudinal layer Fig. 26.9

Fig. 26.9 Serosa or adventitia Areolar connective tissue with collagen and elastic fibers Serosa is covered with visceral peritoneum Adventitia is outside peritoneum Serosa Lumen

Fig. 26.9 Blood vessels, lymphatic vessels, and nerves enter from adjacent organs or mesentery Blood vessels fenestrated capillaries within mucosa layer veins in mucosa anastomose in submucosa then exit Mesentery Vein Artery Lymph vessel Lumen

Lymph vessels and tissues Fig. 24.2 Lymph vessels and tissues Lacteal is blind-end lymphatic capillaries within villus of small intestine Absorb fats and fat-soluble vitamins Lymphatic capillaries form lymphatic vessels outside organ walls Many lymph nodes near organs and within mesentery Lymph transported to cisterna chyli then thoracic duct Interstitial fluid Capillary bed Venule Lymphatic capillaries Tissue cells Arteriole Lacteals (a) Capillary bed and lymphatic capillaries

(a) Pharynx and esophagus Diaphragm Stomach Inferior esophageal sphincter Esophageal hiatus Esophagus Superior esophageal Laryngopharynx Oropharynx Esophagus Fig. 26.10 ~25cm long, mostly within thorax; between trachea and vertebrae Connects to pharynx at superior esophageal sphincter closed during inhalation Connects to stomach at esophageal hiatus works with diaphragm to prevent reflux from stomach

Acid reflux Copyright © McGraw-Hill Education. Permission required for reproduction or display. Page 790 Reflux esophagitis is pain and irritation of esophagus from stomach acid more common in smokers, overweight people, overeaters Gastroesophageal reflux disease (GERD) = erosion and scarring of esophageal tissue more advanced cases become Barrett esophagus increases chance of cancer Barrett esophagus (a) Endoscopic view of a normal esophagus. (b) An endoscopic view of the esophagus shows the signs of Barrett esophagus.

Esophagus does not absorb nutrients Fig. 26.10 (b) Esophagus, transverse section Esophagus does not absorb nutrients Mucosa has thick, nonkeratinized stratified squamous epithelium withstands abrasions of bolus Submucosa has lots of elastic fibers stretches during swallowing mucous glands provide lubricating mucus Muscularis has two layers skeletal and smooth muscles skeletal muscle contracts and returns to shape faster Mucosa Muscularis mucosae Submucosa Muscularis Adventitia LM 11x Stratified squamous epithelium Mucosa Lamina propria Muscularis mucosae LM 65x (c) Esophageal mucosa