• take in food
• break it down into nutrient molecules
• absorb molecules into bloodstream
• rid body of any indigestible remains
  Digestive processes
• 1. ingestion: eating
• 2. Propulsion: movement of food through alimentary canal
• 3. Mechanical breakdown: includes chewing, mixing food with saliva, churring food in stomach, segmentation
• 4. Digestion: series of catabolic stepts that involves enzymes that break down complex food molecules into chemical building blocks
• 5. Absorption: passage of digested fragments from lumen of GI tract into blood or lymph
• 6. Defaciton: elimination of indigestible substances via anus in form of feces
     

1. Mucosa

• tunic layer that lines lumen
• Functions: different layers perform 1 or all 3
• secretes mucus, digestive enzymes, hormones
• absorbs end products of digestion
• protects against infectious disease

2. Submucosa

• consists of areolar connective tissue
• contains blood and lymphatic vessels, lymphoid follicles, submucosal nerve plexus that supply surrounding GI tract tissues
• abundant amount of elastic tissues, help organs regain shape after storing large meal
• 3.Muscularis Externa
• muscle layer responsible for segmentation and peristalsis
• contains inner circular muscle layer and outer longitudinal layers
• Circular layers thickens in some areas to form sphincters

4. Serosa

• outermost layer, made up of visceral peritoneum

• organs fall into 2 groups:

1. Alimentary canal

• continuous muscular tube that runs from the mouth to anus
• digests food: breaks down into smaller fragments
• Absorbs fragments through lining into blood
• organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

2. Accessory organs:

• teeth, gallbladder, tongue, digestive glands: produce secretions that help breakdown food, salivary glands, liver, pancreas

• mouth is where food us chewed and mixed with enzyme- containing saliva that begins process of digestion, and swallowing process is initiated
• associated organs: mouth, tongue, saliving glands, teeth
• Mouth ( oral cavity)
• oral orifice us anterior opening
• Walls of mouth lined with stratified squamous epithelium
• Lips and cheeks
• lip composed of fleshy orbicularis oris muscle
• cheeks: composed of buccinator muscles
• hard palate: formed by palatine bones and palatine processes of maxilla with a midline ridge calle raphe
  
  • soft palate: fold formed mostly of skeletal muscle
• closes off nasopharynx during swallowing
• Tongue
• occupies floor of mouth
• Functions: gripping, repositioning, mixing of food during chewing
• formation of bulus, mixture of food and saliva
• initiation of swallowing speech and taste
  

The pharynx

• food passes from mouth into oropharynx and then into larypharonyx
• allows passage of food, fluids, and air
• external muscle layers consists of two skeletal muscle layers
  The esophagus
• flat muscular tube that runs from laryngopharynx to stomach
• is collapsed when not involved in food propulsion
  Stomach
• temporary storage tank that starts chemical breakdown of protein digestion
• converts blood of food to paste-like chyme
• empty stomach has 50 ml volume but can expand to 4l
• liver: digestive function is production of bile
• bile: fat emulsifier
• gallbladder: chief function us storage of bile
• pancreas: supplies most of enzymes needed to digest chime, as well as bicarbonate to neutralize stomach acid
  The liver
• largest gland in the body
• consists of 4 primary lobes: right, left, caudale, quandrate

Gallbladder

• thin-walled muscular sac on ventral surface of liver
• functions to store and concentrate bile by absorbing water and ions
  pancreas
• exocrine function: productive pancreatic juice
• Endocrine function: secretion of insulin and glucagon by pancreatic juices

• Renal corpuscle
• 1. glomerular- tuft of capillaries composed of fenestrated endothelium
• highly porous capillaries
• allows for efficient filtrate formation

2. Glomerular capsule

• cup shaped, hollow structure surrounding glomerulus
• consists of 2 layers
• parietal layer: simple squamous epithelium
• visceral layer: clings to glomerular capillaries; branching epithelial podocytes
  

• structural and functional units that forms urine in the kidneys
• 1 million m=per kidney
• 2 main parts: renal capsule, renal tubule

• Renal tubule is about 3 cm long
• consists of single layer of epithelial cells, region has its own unique histology and function
  3 major parts
• Proximal convoluted tubule- proximal, closest to renal corpuscle
• nephron loop
• distal convoluted tubule
• distal, farthest from renal corpuscle
• distal convoluted tubule drains into collecting duct