ch 26 Digestive system

Food mixed with saliva- bolus

bolus is sufficiently mixed with gastric juice in stomach = chyme

GI tract

•Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus

Accessory

•Teeth, tongue, salivary glands, liver, gallbladder, and pancreas

•Ingestion-food in mouth

•Motility contractions that mix and move materials

-Peristalsis muscular contraction that move

-Mixing (segmentation) small intestine combine with digestive secretions

•Secretion- mucin or fluids such as acid, bile, or digestive enzymes

•Digestion- break into small structure -Mechanical (mastication). chemical (enzyme)

•Absorption- into blood or lymph

•Elimination of wastes- defecation, feces

nonkeratinized stratified squamous epithelium

•Teeth & lips anteriorly; oropharynx posteriorly

•Palate superiorly; mylohyoid muscle inferiorly

Two regions

•Vestibule between cheeks or lips and gums (candy)

•Oral cavity proper central to alveolar processes of jaw bones

gingivae (gums) cover alveolar processes of teeth

lips to gum, midline mucosa fold labial frenulum

Anterior hard palate

•transverse palatine folds, bumps on top

Posterior soft palate

• uvula, elevates during swallowing and closes entrance to nasopharynx

•Palatoglossal arch (anterior)

•Palatopharyngeal arch (posterior)

palatine tonsils between the two arches

skeletal muscle

papillae (small projections)

compress food into bolus

attached to floor by lingual frenulum

Posteroinferior surface lingual tonsils

produce saliva

• food become bolus

•chemical digestion of carbohydrates with amylase

•Antibacterial with lysosyme

taste receptors can be stimulated

Unicellular,

small amount of saliva

saliva contains lingual lipase

•Parotid glands (largest, 25%, below ear)

parotid duct parallel to zygomatic arch

•Submandibular glands (inferior, 70%Submandibular duct papilla floor of the mouth)

•Sublingual glands( inferior tongue, •sublingual ducts inferior surface

•Mucous cells: secrete mucin, which forms mucus upon hydration

•Serous cells: secrete fluid with ions, lysozyme, and salivary amylase

teeth or dentition

crown, neck, roots

Roots fit into dental alveoli (sockets) and are connected to jaw bone with periodontal ligaments

•Each root is covered with cementum

Crown is formed by tough enamel

Dentin mass of a tooth

pulp with blood vessel and nerve

opens at apical foramen

•20 deciduous teeth (milk teeth) 30 months

•32 permanent teeth

Permanent teeth

•Incisors: most anterior, slicing

•Canines: puncturing

•Premolars: flat crowns with(cusps) grinding

•Molars: thickest and most posterior teeth, grinding

Each quadrant has two incisors, one canine, two premolars, and three molars (wisdom tooth is third molar)

(throat) muscular tube

Oropharynx and laryngopharynx- nonkeratinized stratified squamous

Superior, middle, and inferior pharyngeal constrictors

•CN X

external carotid arteries supply

Internal jugular veins drain

•Parietal peritoneum body wall

•Peritoneal cavity between 2 layers

•Visceral peritoneum covers internal organs

Organs surrounded by visceral peritoneum (stomach)

lie "behind" the peritoneum, posterior abdominopelvic wall( pancreas, rectum)

-folds of peritoneum, support intraperitoneal GI tract organs

-Blood vessels, lymphatic vessels, and nerves supply the digestive organs

•Greater omentum greater curvature of stomach and covers most abdominal organs

•Lesser omentum lesser curvature of the stomach and duodenum to the liver

• mesentery proper suspends small intestines from posterior abdominal wall

•mesocolon attaches large intestine to posterior abdominal wall

folds of peritoneum that connect structures

•Coronary ligament (liver to diaphragm),

falciform ligament -between liver(liver to abdominal wall),

lienorenal ligament (spleen to kidney)

•Mucosa

•Submucosa

•Muscularis

Adventitia or serosa

mucus-producing epithelial tissue

•areolar connective tissue layer lamina propria

•smooth muscle muscularis mucosae

*GI wall deep

•Areolar / dense irregular connective tissue

•Lymphatic ducts

•Mucin-secreting glands

•Blood vessels

•submucosal nerve plexus

*GI wall

•2 smooth muscle:

•Inner circular layer: Constricts lumen and forms sphincters

-Myenteric nerve plexus- Nerve and associated ganglia between layers of muscles

•Outer longitudinal layer: Shortens the tube

*GI wall

Outermost layer of GI tract wall

adventitia areolar CT with collagen and elastic fibers

Serosa same, but covered by visceral peritoneum

•Celiac trunk

•Superior mesenteric artery

•Inferior mesenteric artery

(lymphatic capillaries) in villi of small intestine

Lymph ducts transport lymph to the cisterna chyli, which drains into thoracic duct

in appendix and small intestine (aggregate nodules called Peyer patches)

autonomic plexuses follow unpaired artery:

•Celiac plexus

•Superior mesenteric plexus

•Inferior mesenteric plexus

parasympathetic-promotes digestive secretion and motility

-pharynx to stomach

-through diaphragm, esophageal hiatus before connecting to stomach

-anterior the vertebral bodies

Esophageal mucosa -stratified squamous epithelium

Submucosa - many elastic fibers and mucous glands

Muscularis - both skeletal and smooth muscle

•Transitions from skeletal muscle (voluntary) to smooth muscle

•Superior esophageal sphincter: ring of skeletal muscle top of esophagus; closes during inhalation

•Inferior esophageal sphincter: ring of smooth muscle at bottom of esophgus; prevents regurgitating from stomach

•Voluntary phase -mouth

•Pharyngeal phase bolus enters oropharynx and involves involuntary swallowing reflex controlled by medulla oblongata

•Esophageal phase 5 to 8 s when bolus, esophagus to stomach

upper left quadrant of abdomen

mechanical and chemical digestion

bolus processed into chyme

•Cardia: meets esophagus at cardiac orifice

•Fundus: Dome-shaped next to cardiac orifice

•Body: Largest

•Pylorus: stomach meet small intestine

-Includes pyloric antrum and pyloric canal

-Smooth muscle pyloric sphincter controls opening to duodenum (pyloric orifice)

greater lesser curvature

Internal surface gastric folds (rugae)

simple columnar epithelium

depressions gastric pits

digestive juice-producing gastric glands

•Surface mucous cells secrete alkaline fluid with mucin

•Mucous neck cells secrete acidic fluid containing mucin

•Parietal cells secrete hydrochloric acid and intrinsic factor

•Chief cells secrete pepsinogen (converted into pepsin in stomach lumen)

•Enteroendocrine cells secrete hormones gastrin

finish chemical digestion, most nutrient absorption

12 hr

shorter in living person

•Duodenum

•Jejunum

•Ileum

•Originates at pyloric sphincter after stomach

•Contains major duodenal papilla, bile(liver) and pancreatic secretions enter GI tract

•Minor duodenal papilla receives small pancreatic juice

meet duodenum at duodenojejunal flexure

•middle small intestine

•primary chemical digestion and nutrient absorption

•last small intestine, absorb leftover nurtrients

• terminates at ileocecal valve, sphincter that controls entry into large intestine

 simple columnar epithelium-

mucosal and submucosal tunics folds circular folds (plicae circularis)

- villi and microvilli on circular folds

•Collectively appear as a brush border

Intestinal glands between villi are invaginations of mucosa , release hormones, mucus, digestive enzyme

Submucosal glands of duodenum produce alkaline mucus

-around small intestine

-Absorbs fluids/water and ions and compacts undigestible wastes into feces (store until defecation)

•Cecum

•Ascending colon

•Transverse colon

•Descending colon

•Sigmoid colon

•Rectum

•Anal canal

first part of large intestine

sac in lower right quadrant

•Vermiform appendix -fingerlike with lymphatic nodules results in appendicitis,

•Ileocecal valve between small and large intestine

upward from cecum, right lateral border of abdomen

•Near liver, 90° turn toward the left; right colic flexure (hepatic flexure)

approaches the spleen

•suspended by transverse mesocolon

• 90° turn at spleen left colic flexure (splenic flexure)

down the left side of the abdomen

letter S

•start at sigmoid flexure

It turns inferomedially and is suspended by the sigmoid mesentery

•terminates as the rectum

store fecal material until defecation

•three transverse folds, rectal valves, that ensure fecal is retained during passage of gas

•terminates at the anal canal

last centimeters of large intestine

•passes through levator ani muscles of the pelvic floor

•Anal columns line internal surface of the anal canal

•Anal sinuses secrete mucin for lubrication during defecation

•Internal and external anal sphincters relax during defecation

mucosa lined with simple columnar epithelium with goblet cells (Secrete mucin lubricate fecal)

• rubber band teniae coli

• sacs, haustra

•Lobules of fat omental appendices

Gastroileal reflex: Ingestion of food increases peristaltic movements in ileum

Peristaltic movements weak and sluggish

Haustral churning occurs after haustrum fills stimulating reflex contractions in muscularis

Mass movements powerful peristaltic-like contractions involving teniae coli

-Occur after a meal in gastrocolic reflex

•Constipation: impaired ability to defecate; feces hard to eliminate

•Diarrhea: Excessive water in intestinal lumen, watery feces

•Liver

•Gall bladder

•Pancreas

•Biliary apparatus

right quadrant of abdomen

•Right (largest)and left lobes

•Separated by falciform ligament

•Caudate lobe and quadrate lobe subdivisions of right lobe

Round ligament of the liver remnant of umbilical vein

•Ligamentum venosum (remnant of embryonic ductus venosus)

• caudate lobe

• Gall bladder

•Inferior vena cava

•Porta hepatis: vessels, bile ducts, and nerves enter

hepatocytes

•At periphery of lobule are several portal triads: hepatic portal vein, hepatic artery, and bile duct

•Central vein middle of lobule, drain

-Hepatic portal vein nutrient-rich blood to liver

-Hepatic artery proper oxygen-rich blood to liver; left and right hepatic arteries

-Hepatic veins empty into inferior vena cava

leaky capillaries lined with reticuloendothelial cells, phagocytes with an immune function

Hepatocytes absorb nutrients and produce bile

•bile canaliculi bring bile to bile duct in portal triad

inferior of liver

store and concentrate bile

Cystic duct connects gall bladder to common bile duct

neck, body, and fundus

thin ducts that transport bile from liver and gall bladder to duodenum

-portal triad

-Left and right lobes of liver drain into left and right hepatic ducts

-merge to common hepatic duct

- cystic duct and common hepatic duct merge to common bile duct

The common bile duct and main pancreatic duct merge to form the hepatopancreatic ampulla

•Enters duodenum at major duodenal papilla

•Endocrine functions by pancreatic islets

•Exocrine functions by acinar cells secreting pancreatic juice (pancreatic amylase- break starch, neturalize) into duodenum via main (and accessory) pancreatic duct

head, body, and tail

decrease

-digestive secretions

-internal protection by mucus

-chemical digestion (less nutrient)

-Epithelial cells replaced slowly

-thickness of GI tract wall decreases

-periodontal disease and teeth loss

-olfactory and gustatory sensations

third week

gut tube

Liver bud

Pancreas starts Week 4

During Week 5 primary intestinal loop

muscular contraction that move food

inner oblique layer, middle circular layer, and outer longitudinal layer. 

epatic portal vein, hepatic artery, and bile duct