ANAPH111

• The functions of the Digestive System include Ingestion and Mastication, Propulsion and Mixing, Digestion and Secretion, Absorption, and Elimination.
• The Digestive System is composed of the digestive or gastrointestinal tract which includes the oral cavity, pharynx, esophagus, stomach, small and large intestines, anus, and specific organs such as the salivary glands, liver, pancreas, oral cavity and esophagus are lined with stratified epithelium, which protects them from the abrasion of chewing and swallowing.
• The stomach and intestine are lined with columnar epithelium, which is specialized for secretion of digestive fluids and absorption of nutrients.
• The Digestive Tract consists of four layers or tunics: the mucosa, the submucosa, the muscularis, and a serosa or an adventina.
• The mucosa is the innermost layer of the Digestive Tract and consists of three layers: muscularis mucae, lamina propria, and mucous epithelium.
• Cortical nephron have renal corpuscles distributed throughout the cortex.
• Renal corpuscle is the filtration portion of the nephron and consists of glomerulus, a network of capillaries twisted around Bowman capsule.
• Long loops of Henle, which extend deep into the medulla, are a characteristic of juxtamedullary nephron.
• Papillary duct is located near the tip of the renal papilla that empties into a calyx and is formed by several collecting ducts merging into a larger-diameter tubule.
• Only 15% of nephrons are juxtamedullary nephron.
• Loops of Henle in cortical nephron are shorter than those of juxtamedullary and are closer to the outer edge of the cortex.
• Longer loops of Henle are well adapted for water conservation.
• There are two types of nephrons: juxtamedullary and cortical nephrons.
• Juxtamedullary nephron have renal corpuscles that are found deep in the cortex near the medulla.
• The submucosa is a thick layer of loose connective tissue containing nerves, blood vessels, and small glands.
• The muscularis consists of an inner layer of circular smooth muscle, an outer layer of longitudinal smooth muscles, and composes the enteric nervous system along with the nerve plexuses of submucosa.
• The serosa is the outermost layer of the Digestive Tract and consists of peritoneum, parietal peritoneum, and adventitia.
• The peritoneum linings and covers the organs of the abdominal cavity and provides a route for blood vessels and nerves from the abdominal wall to the organs.
• The peritoneum consists of two layers of serous membranes with a thin layer of loose connective tissue between them.
• Specific mesenteries include mesentery proper, lesser omentum, greater omentum, and omental bursa.
• The enteric nervous system is an extensive network of submucosal and myenteric plexuses within the walls of the GIT.
• The liver, the largest internal organ of the body, is located in the right upper quadrant of the abdomen and consists of four lobes: right lobe, left lobe, caudate lobe, and the quadrate lobe.
• The blood capillary network and the lacteal are very important in transporting absorbed nutrients.
• The mucosa and submucosa of the digestive tract form a series of circular folds that run perpendicular to the long axis of the digestive tract.
• Tiny, fingerlike projections of the mucosa, called villi, are covered by a simple columnar epithelium and contain a blood capillary network and a lymphatic capillary called lacteal.
• The liver receives blood from two sources: the hepatic artery, which delivers oxygenated blood to the liver, and the hepatic portal vein, which carries nutrient-rich blood from the digestive system tract to the liver.
• The falciform ligament separates the right and left lobes of the liver.
• The hepatic veins are the exit point of the blood before emptying into the inferior vena cava.
• The liver is divided into hepatic lobules.
• Peristaltic contractions proceed along the length of the intestine for variable distances and cause the chyme to move along the small intestine.
• Mucus is produced by duodenal glands and goblet cells.
• The porta is where blood vessels, ducts, and nerves enter or exit the liver.
• Segmental contractions are propagated for only a short distance and mix intestinal contents.
• Epithelial cells are located within tubular glands of the mucosa called intestinal glands or crypts of Lieberkuhn at the base of the villi.
• Cytoplasmic extensions of the epithelium, called microvilli, increase the surface area of the mucosa of the small intestine about 600-fold.
• Hepatocytes are the functional units of the liver and take up nutrients from the portal blood.
• The mucosa of the small intestine is lined by simple columnar epithelium with four major cell types: absorptive cells, goblet cells, granular cells, and endocrine cells.
• The oral cavity is divided into two regions: the space between the lips or cheeks and the teeth, and the oral cavity proper, which lies inside the teeth and houses the tongue.
• Primary teeth, also known as milk or baby teeth, are lost during childhood and are replaced by the permanent teeth, also called as secondary teeth, between 5 to 11 years.
• Tongue moves food in the mouth and, in cooperation with the cheeks and lips, holds the food in place during mastication.