AHE II 3.3 - DIGESTIVE PART 2

• Course objective: Explore how the body obtains nutrients, expels waste by tracing anatomical structures, and their roles, through the body.

Blood Supply and Innervation

• Visually identify blood supply and innervation to the oral cavity, pharynx, esophagus, stomach, small and large intestines.

Digestive Anatomy and Function

• Identify and describe digestive function and anatomy, like muscles, vessels, innervation, and structures of salivary glands.

Teeth Anatomy

• Recall basic anatomy of teeth including structures, blood supply, innervation and various types.

Liver Functions

• Recall functions and anatomy of the liver
• Describe blood supply to the liver and its relation to the hepatic portal system
• Link liver functions with histological organization like hepatic lobules, hepatocytes, hepatic sinusoids

Gallbladder

• Recall function, anatomy, and blood supply of the gallbladder

Biliary Apparatus

• Trace and describe how secretory products travel through the biliary apparatus

Pancreas

• Recall anatomy and primary blood supply of the pancreas
• Compare and contrast pancreatic acinar cell function
• Explain how secretions in the pancreas are stimulated

Arterial Supply to Oral Cavity and Pharynx

• Branches from the external carotid and subclavian arteries supply blood.
• External carotid artery has multiple branches, including:
  • Ascending pharyngeal artery
  • Lingual artery
  • Facial artery
  • Maxillary artery
• Subclavian artery branches include:
  • Thyrocervical trunk
• The thyrocervical trunk further branches into the inferior thyroid artery and pharyngeal branches.

Venous Drainage from Oral Cavity and Pharynx

• Drains into internal and/or external jugular veins from:
  • Pterygoid plexus
  • Maxillary vein
  • Retromandibular vein
  • Facial vein
  • Lingual vein
  • Internal jugular vein
• Pharyngeal venous plexus also contributes to venous drainage.

Blood Supply to Esophagus

• Arises from adjacent vessels including:
  • Inferior thyroid artery
  • Bronchial arteries
  • Descending aorta
  • Left gastric artery

Blood Supply to Stomach

• Left and right gastric arteries supply blood
• Gastroduodenal artery supplies blood
• Splenic artery supplies blood
• Left and right gastro-omental arteries supply blood

Blood Supply to Small Intestine

• Superior mesenteric artery is the main blood supply to the small intestine.
• Gastroduodenal artery supplies blood
• Ileocolic artery supplies blood
• Ileal arteries supply blood
• Jejunal arteries supply blood

Blood Supply to Large Intestine

• Superior and inferior mesenteric arteries supply blood.
  • Middle colic artery
  • Right colic artery
  • Ileocolic artery
  • Superior rectal artery
  • Middle rectal artery
  • Inferior rectal artery
  • Left colic artery
  • Sigmoid arteries

Innervation to Esophagus

• Vagus nerves and sympathetic trunk branches form the esophageal plexus.
• Sensory Afferent nerves:
  • Vagus nerve mediates reflexes and physiological processes
  • Sympathetic trunk and splanchnic nerves transmit pain
• Efferent nerves that control swallowing reflex:
  • Vagus nerve has anterior and posterior vagal trunks
  • No sympathetic activity

GI Tract Innervation: Autonomic

• Sympathetic Innervation:
  • Spinal nerves T5-L1 innervate the GI tract, with L2/3 extending to pelvic viscera.
  • Thoracic and lumbar splanchnic nerves play a role.
  • Prevertebral ganglia: stomach, proximal large intestine, and intestine/rectum
  • Innervation through postganglionic fibers to organs
• Parasympathetic Innervation:
  • Vagus nerve (CN X) innervates the esophagus through the left colic flexure.
  • Pelvic splanchnic nerve innervates the left colic flexure through the superior rectum.
• Autonomic abdominal plexuses: celiac, superior and inferior mesenteric plexuses
• Pain through visceral pain innervation.

GI Tract Innervation: Enteric

• Ganglionic nerve plexus lies entirely within the gut wall from the esophagus to the anus.
• Myenteric Plexus:
  • Located between outer longitudinal and inner circular layers of the muscular layer.
  • Coordinates motility.
• Submucosal Plexus:
  • Exists between the muscularis and submucosal layers.
  • Regulates secretions, blood flow, and absoprtion.

Accessory Digestive Organs

• Head:
  • Tongue
  • Teeth
  • Salivary glands
• Abdomen:
  • Liver
  • Gallbladder
  • Pancreas

Salivary Glands

• Produce and secrete saliva fluid to assist in digestion, amounting to 1 to 1.5 liters/day.
• Functions include moistening food, initiating chemical digestion, defense via antibodies/lysozyme, and taste.
• Types of salivary glands:
  • Parotid
  • Submandibular
  • Sublingual

Parotid Gland

• Largest salivary gland
• Extends over the masseter muscle
• Parotid duct penetrates the buccinator muscle and opens adjacent to the 2nd upper molar.
• Parasympathetic innervation via CN IX (glossopharyngeal nerve)
• Secretes serous fluids containing ions, lysozyme, and salivary amylase.

Submandibular and Sublingual Glands

• Produce majority of saliva.
• The submandibular duct opens into the floor of the mouth.
• Multiple sublingual ducts open into the inferior surface of the oral cavity.
• Parasympathetic innervation via CN VII (facial nerve) through the chorda tympani
• Secrete serous fluids and mucin (via mucous cells), forming mucus upon hydration.

Teeth

• Responsible for mastication.
• Sit in alveoli (sockets) in alveolar arches (elevated arches of bone)
• Distinguished based on morphology, position, and function:
  • Incisors (2)
  • Canines (1)
  • Premolar (2)
  • Molars (3)
• Two successive sets:
  • Deciduous teeth emerge between 6 months and 2 years (n=20)
  • Permanent teeth emerge between 6-25 years (n=32)
• Gingiva:
  • Specialized oral mucosa that surrounds the teeth and covers adjacent regions of alveolar bone.

Teeth Structures

• Three Regions:
  • Root
  • Neck
  • Crown
• Key Components:
  • Enamel: forms crown, hardest material
  • Dentin: main tooth component
  • Cementum: hardened material around root
  • Periodontal ligaments: bind roots into alveoli
  • Pulp cavity: central space filled with CT.
  • Root canal: space in the root filled with pulp
• Blood Supply: External carotid gives rise to maxillary that eventually gives rise to superior/inferior alveolar.
• Innervation: All branches to teeth and gingiva are from CN V (trigeminal).

Liver Functions

• Located in the right upper abdominal quadrant
• Comprised of 4 lobes and supported by 2 ligaments
• Functions:
  • Produce bile
  • Detoxify drugs, metabolites, and poisons
  • Store excess and release nutrients and vitamins
  • Synthesize blood plasma proteins: albumins, globulins, fibrinogen
  • Phagocytize debris in blood

Liver Anatomy

• Diaphragmatic Surface: lies against the inferior surface of the diaphragm.
• Subphrenic Recess: Located between the liver and diaphragm.
• Visceral Surface: covered with visceral peritoneum.
• Hepatorenal Recess: Located between the liver, right kidney, and suprarenal gland.
• Right (R) and left (L) and divided by falciform ligament (peritoneal fold)
• Right Lobe -> Quadrate and Caudate
• Visceral -> Hepatic aa & Hepatic Portal Vien & Hepatic Ducts
• Contains the porta hepatis

Liver- Blood Supply

• Arteries:
  • Celiac trunk
  • Common hepatic artery
  • Hepatic artery proper
  • Left and right hepatic arteries
  • Rich in oxygen
• Veins:
  • Hepatic portal vein drains from GI tract, pancreas, and spleen.
  • Accounts for 75% of blood into the liver
  • Rich in nutrients, but poor in oxygen
• Hepatic veins drain into the inferior vena cava.
• Portal venous blood allows the liver to perform metabolic functions. Specifically, portal venous blood is rich in nutrients, but lacks oxygen
• Arterial supply to the liver supplies oxygen to hepatocytes and supporting liver cells.
• Blood from arteries and veins mix in hepatic lobules and will exit liver through hepatic vein

Liver Histology

• Comprised of hepatic lobules organized around a central vein.
  • Each liver cells (hepatocytes) will each take their respective action
  • Hepatocytes- epithelial cells arranged in long plates
  • Hepatic sinusoids exist, and are the spaces between plates of hepatocytes
  • Sinusoids will be on the periphery of the CT

Liver-Hepatic Portal System

• Key Landmarks
  • Common heaptic ducts
  • Hepatic Portal Vein
  • Hepatic Artery
• All will become branch further and liver
• Blood from arteries and veins mix in heaptic lobules
• Blood will exit liver and travel through Hepatic Veine
• Bile will exit in Biliary System through Common heaptic duct

Gallbladder

• Concentrates and stores bile produced by the liver.
• Pear-shaped sac that lies on the visceral surface of the right liver lobe.
• Regions:*
• Fundus
• Body
• Neck
• Arterial supply via cystic artery from the right hepatic artery.
• Left and Right Heaptic leave the liver to form the Ducts
• Ducts merges with cystric duct entering gallbladder
• Ducts will merge to form the Common Bile

Gallstones

• Found in 10% of those over 40
• More common in women
• Comprised of cholesterol and bile
• Can lodge at the neck of gallbladder and severe pain
• Cholceystecomy is the removal of gallbladder.
• Cholecystitis is the inflammation which can cause paint in the right shoulder.

Pancreas

• Functions
  • Heterocrine gland both endocrine and exocrine
• Posterior to Stomach.
• Comrised of 4 region
  • Head - Main function of the Process
  • Neck
  • Body- Enlongated Nodular Organ
  • Tail
• Contains both the pancreatic ducts: bile, liver, and gall
• Heterocrine gland has both endocrine and exocrine funcitons.

Pancreas-Cells

• Exocrine functions relates to pancreastic juicies ( digestive Enzyme)
• Comrised of Acinar cell ( modified Epithlial cells)
• Acanar Cells -> Help neautilize in the duodenum - > Aid withdigestion
• Secretion-> Communication & Para Sympathic Function