Digestive System

Digestive System

Stomach

• Location: Located in the epigastric region, slightly shifted to the left.

• Relations:

• Anterior: Anterior abdominal wall, liver.

• Posterior: Pancreas, duodenum.

• Divisions:

• 1. Cardia: Includes the cardiac notch + cardiac orifice.

• 2. Fundus.

• 3. Body.

• 4. Pyloric antrum: Site of HCl secretion.

• 5. Pyloric orifice: Formed by the pyloric sphincter, opens and closes based on the pH difference between the stomach and duodenum.

• Layers:

• 1. Mucosa: Contains numerous gastric glands.

• 2. Submucosa.

• 3. Muscularis propria: Oblique – circular – longitudinal.

• 4. Subserosa.

• 5. Serosa.

• Pyloric sphincter: Thickened circular muscle.

• Capacity:

• Newborn: 30 ml.

• Puberty: 1000 ml.

• Adult: 1500 ml.

• Blood supply:

• Mainly from the celiac trunk.

• Lesser curvature:

• Left gastric artery: Branches off the celiac trunk.

• Right gastric artery: Branches off the proper hepatic artery.

• Greater curvature:

• Left gastro-omental artery: Branches off the splenic artery.

• Right gastro-omental artery: Branches off the gastroduodenal artery.

• Fundus:

• Short gastric arteries.

• Posterior gastric artery.

• Nerve supply:

• Celiac plexus.

• Vagus nerve (X).

Small Intestine

• Length: 6-7 meters.

• Parts:

• Duodenum.

• Jejunum: 2/5 proximal.

• Ileum: 3/5 distal.

Duodenum

• Characteristics:

• 25 cm long, shortest, widest.

• No mesentery, covered by peritoneum on the anterior surface.

• Site where the bile duct + pancreatic duct enter.

• 4 parts:

• Superior – descending – transverse – ascending.

• Superior part of the duodenum:

• 5 cm long.

• Mobile.

• Descending part of the duodenum:

• 8 cm long.

• Minor duodenal papilla: Where the accessory pancreatic duct opens.

• Major duodenal papilla: Where the main pancreatic duct + common bile duct open.

• Transverse part of the duodenum: 10 cm long.

• Ascending part of the duodenum: 2.5 cm long.

• 4 layers:

• Serosa.

• Muscularis propria: Inner circular, outer longitudinal.

• Submucosa.

• Mucosa.

Jejunum:

• Characteristics:

• Diameter: 4 cm.

• Located in the umbilical region.

• Thick wall, red, rich in blood vessels.

• Numerous mucosal folds.

• Hardly any lymph nodes.

Ileum:

• Characteristics:

• Diameter: 3.5 cm.

• Located in the hypogastric and iliac regions.

• Thin wall, many lymph nodes.

• Blood supply: Superior mesenteric artery.

Large Intestine

• Length: 1.5 meters.

• Parts:

• Ascending colon: 15 cm.

• Transverse colon: 50 cm.

• Descending colon: 25 cm.

• Sigmoid colon: 40 cm.

Cecum

• Characteristics:

• Located in the right iliac fossa.

• Height: 6 cm, width: 7.5 cm.

• Behind it is the ileocecal recess – appendix.

Appendix

• Characteristics: Narrow tube, worm-shaped.

• Location:

• Behind the cecum, below the ascending colon.

• Suspended on the pelvic brim, close to the right fallopian tube and ovary.

• Below the cecum.

• In front or behind the terminal ileum.

Cecum – Rectum – Anal Canal: Diameter gradually decreases then widens.

Large intestine vs. Small intestine:

• Larger diameter.

• More fixed position.

Anal sphincter:

• Internal:

• 3/4 of the upper anal canal.

• Smooth muscle.

• External:

• Entire anal canal.

• Striated muscle.

Hemorrhoids: Dilated venous plexus.

• Internal:

• Superior rectal venous plexus.

• Covered by mucosa.

• External:

• Inferior rectal venous plexus.

• Covered by skin.

Liver

• Location: Right hypochondriac region + epigastric region.

• Weight:

• Male: 1.4 – 1.8 kg.

• Female: 1.2 – 1.4 kg.

• Parts:

• Diaphragmatic surface (convex).

• Visceral surface (flat).

• Inferior border.

Diaphragmatic surface:

• Protrudes anteriorly, superiorly, and to the right.

• Upper, right, anterior, and posterior parts (bare area).

• Falciform ligament: Divides the liver into two lobes: right and left.

• Anterior part:

• In the subcostal angle.

• Examination method: Percussion.

• Upper part: Contains the cardiac impression.

• Posterior part:

• Bare area.

• Above and below: Layers of the coronary ligament.

• Left: Groove for the inferior vena cava.

• Right part: Diaphragmatic dome separates it from the lung and ribs 7 to 9.

Visceral surface:

• Flat, inferior, posterior, and to the left.

• 4 lobes: right, left, caudate, and quadrate.

• Right lobe:

• Impression of the colon (right colon).

• Renal impression.

• Duodenal impression (superior duodenal flexure).

• Suprarenal impression.

• Left lobe:

• Esophageal impression.

• Gastric impression.

• Caudate lobe:

• Right caudate process.

• Left papillary process.

• Quadrate lobe: Pyloric impression.

• Parts not covered by peritoneum:

• Porta hepatis.

• Ligamentum teres fossa.

• Fossa of the gallbladder.

• Inferior border: Has the ligamentum teres notch.

Liver receives blood from:

• Common hepatic artery –> Proper hepatic artery –> Right hepatic artery + Left hepatic artery.

Portal vein is formed by the union of veins:

• Superior mesenteric vein.

• Splenic vein.

Porta hepatis from anterior to posterior:

• Bile duct – Portal vein – Hepatic artery.

Infection of the inferior mesenteric vein, splenic vein: Left lobe of the liver.

Infection of the superior mesenteric vein: Right lobe of the liver.

Rib fracture: Penetrates the diaphragm –> Liver rupture.

Parotid gland

• Characteristics:

• Largest, weighs 25 g.

• Parts: superficial, deep, duct, accessory parotid gland.

• Pyramid shape: 1 apex, 1 base, 3 surfaces.

• Relations:

• External carotid artery (passes through the upper jaw + superficial temporal).

• Nerves (most superficial).

• Opening of the parotid duct: Opposite the 2nd upper molar.

Submandibular gland

• Characteristics:

• Parts: superficial > deep.

• Mainly secretes serous fluid.

• Relations:

• Superficial: Within the submandibular triangle, includes 3 surfaces.

• Deep: Located between the hypoglossal nerve + sublingual nerve.

• Opening of the submandibular duct: Sublingual caruncle at each end of the sublingual fold.

Sublingual gland

• Characteristics:

• Smallest gland.

• Parts: 8-20 small ducts + 1 large duct.

• Opening of the sublingual duct:

• 8-20 small ducts: Sublingual fold.

• Large duct: Opens together or near the submandibular orifice.

Oral cavity

• Boundaries:

• Anterior + lateral: Gums + dental arches.

• Posterior: Oropharynx – pharynx.

• Roof: Palate.

Gums:

• Soft tissue covering the dental arches.

• 2 parts:

• Free: Around the neck of the tooth.

• Attached: Dental arches on the maxilla and mandible.

Hard palate: Palatine process of the maxilla + horizontal plate of the palatine bone.

Soft palate:

• Muscular, ends with the uvula.

• 2 arches:

• Palatoglossal arch.

• Palatopharyngeal arch.

–> Forms the tonsillar fossa.

Tongue:

• Mass of striated muscle covered by mucosa.

• Oral part: 2/3 anterior, many papillae.

• Pharyngeal part: 1/3 posterior – lingual tonsils.

Vessels of the tongue:

• Lingual artery + Deep lingual artery.

Nerves of the tongue:

• Motor: XII.

• Sensory:

• Anterior to the sulcus:

• General: V3.

• Taste: Chorda tympani.

• Posterior to the sulcus + vallate papillae: IX.

Esophagus

• Characteristics:

• Length: 25 cm.

• 3 parts: Cervical, thoracic, abdominal.

• Lumen has longitudinal folds.

• 4 constrictions:

• Upper end (15 cm).

• Where it crosses the aortic arch (22.5 cm).

• Where it crosses the left main bronchus (27.5 cm).

• Where it passes through the diaphragm (40 cm).

Esophagus (cervical part):

• Lies behind the trachea.

• Recurrent laryngeal nerve loops backward in the groove between the esophagus and trachea.

• Relations: Common carotid artery.

Esophagus (thoracic part):

• Anterior:

• Left main bronchus.

• Trachea.

• Left atrium.

• Posterior:

• Vertebrae.

• Right vagus nerve.

• Thoracic duct.

• Left thoracic aorta.

• Compared to the thoracic aorta:

• Initially: Right, anterior.

• Through the diaphragm: Left, posterior.

Esophagus (abdominal part):

• 2 cm, curves to the left.

• Covered by peritoneum on the anterior + left border.

• Continuous with the cardiac orifice.

Pancreas

• Characteristics:

• Grayish pink.

• 12-15 cm long.

• Parts: Head, Neck, Body, Tail.

Head of the pancreas:

• Left, broad part.

• Anterior: Transverse colon, jejunum.

• Posterior: Inferior vena cava, renal vein, aorta, common bile duct.

Neck of the pancreas:

• Slightly constricted.

• Gastroduodenal artery.

• Mesenteric vein, portal vein.

Body of the pancreas:

• Anterior:

• Covered by peritoneum.

• Related to the stomach.

• Posterior:

• No peritoneum.

• Related to the left kidney.

• Inferior:

• Has peritoneum.

• Related to the duodenojejunal flexure, jejunal loop.

• Anterior border: Related to the transverse mesocolon.

• Superior border: Related to the splenic artery.

Vessels of the pancreas (body + tail): Splenic artery.

Vessels of the pancreas (head):

• Pancreaticoduodenal branches (gastroduodenal artery).

• Superior mesenteric artery.