Digestive system

Gastrointestinal tract

muscular tube running from mouth to anus

functions of GI tract

digest & absorb nutrients

Structure of GI tract

Mouth, Oesophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anus

regions of small intestine (proximal to distal)

Duodenum, jejunum, ileum

nutrient digestion & absorbption

Duodenum

Proximally connected to stomach

Distally connected to the jejunum o

Jejunum

Proximally connected to the duodenum

Distally connected to the ileum

Ileum

Proximally connected to the jejunum

Distally connected to the cecum of the large intestine

Large intestine divisions

cecum, ascending colon, transverse colon, descending colon and sigmoid colon

Caecum

dialated sac at proximal end connectd to the ileum

attached to the appendix

3 regions of the GI tract

foregut, midgut and hindgut

supplied by branches of abdominal aorta

foregut

oesophagus to the proximal half of the duodenum

supplied by celiac trunk

midgut

distal half of duodenum to 2/3 transverse colon

superior mesenteric artery

hindgut

2/3 way along transverse colon to the rectum

inferior mesenteric artery

accessory organs

liver, pancreas, gallbladder and salivary glands

liver

receives 75% blood from portal vein, 25% from hepatic artery drains into IVC

portal triad branch of hepatic artery, portal vein & bile duct

hepatocytes surround central veins & sinusoids

gallbladder

stores & releases bile via cystic duct

pancreas

exocrine acinar cells produce digestive enzymes drain into ducts

endocrine alpha cell secrete glucagon, beta cells secrete insulin

Large intestine

absorbs vitamins & water, breaks down toxins

• Teniae Coli (three longitudinal bands of smooth muscle)

• Haustra (segmented pouches)

• Epiploic appendices (fatty deposits on the surface)

Abdominal aorta

Descending aorta pierces diaphragm at 12th vertebral level becoming the abdominal aorta

celiac trunk

supplies the forgut

superior mesenteric artery

supplies the midgut

inferior mesenteric artery

supplies the hindgut

types of digestion

mechanical

chemical

layers of GI tract wall

mucosa

submucosa

muscularis externa

serosa

upper gastrointestinal tract

oral cavity

pharynx & esophagus

stomach

oral cavity

• Bounded by teeth anteriorly, cheeks laterally, hard/soft palate superiorly, muscular tongue inferiorly, and tonsils posteriorly.

• mechanical and chemical digestion

salivary glands

parotid, submandibular, and sublingual glands.

pharynx & esophagus

Muscular tube in posterior thorax

pierces diaphragm at T10

innervated by esophagal plexus

stomach

J shaped sac in upper-left abdomen

Bound by lower esophageal & pyloric sphincter

rugae (folds) increase SA

3 muscular layers: outer longitudinal, middle circular, inner oblique