Digestive System

• What is the Digestive System's purpose?

  1. Ingestion of food
  2. Physical and chemical digestion of food
  3. Absorption of nutrient molecules
  4. Elimination of undigested remains
• Composed of:

  • Digestive tract 
  • Alimentary canal
  • Digestive glands associated with it
• Liver

  • Largest structure of the body cavity
  • Brown in color
  • 3 lobes
  • Right lobe
  • Left anterior lobe
  • Left posterior lobe
• • Bile
  • Yellow-green
  • Aids in digesting food
  • Digests fats
  • Stored in the gallbladder
  • Goes through the bile duct
• How does bile travel?

  • liver → gallbladder → bile duct → pancreas → intestine
• • Hepatic Lobules
  • Septa 
• • Hepatocytes 
  • Liver cells
  • Stacked on top of each other
  • Arrange in strips; cartwheel
• • Central vein
  • Hepatocytes radiate outward from here
• • Hepatic sinusoids
  • Capillaries that travel between the strips of hepatocytes
  • Drain to the central vein
• • 2 sources of blood for liver
  • Hepatic portal vein
  • Hepatic arteries
• • Hepatic portal vein
  • Major source
  • Carries used blood from the intestine, pancreas, and spleen
• • Hepatic arteries
  • Brings oxygenated blood to the liver
• What is the Portal Triad composed of?

  • Portal vein
  • Hepatic artery
  • Bile duct
• What does the Portal Triad do?

  • Supplies blood to the sinusoids and hepatocytes
• • Septa
  • Connective tissues separating the lobules
  • Consists of hexagonal plate of hepatocytes
• Pancreas Position?

  • Hidden behind the stomach
  • Posterior side
  • Curved along the small intestine
• Parts of the Pancreas?

  • Head of the pancreas 
  • Biggest part of the pancreas
  • Resting along the duodenum
  • Right side of the abdomen
  • Tail of the pancreas 
  • Thin tip
  • Left side of the abdomen
  • Close to the Spleen
  • Body
  • Middle part
• The Pancreas Makes?

  • Trypsin
  • Breaks down proteins
  • Insulin
  • Store glucose from blood stream as glycogen
  • Glucagon
  • Tell cells to release glucose from blood stream
• What is this?

  Pancreas

  
• What is this?

  Liver

  
• Histology of a Pancreas

  
  

  Long line: Lobe

  Big gray circle: Intralobular duct

  White clumps: Islets of langerhans

  Red dots: Pancreatic acini

  
• Histology of a Liver

  Big white: Central vein

  White streaks: Sinusoids

  Violet: Hepatocytes

  Distinct darker pink boundary: Lobule boundary

  Upper left clump: Portal triad

  A)

  B)

  C)

  D)

  E)

  F)

  G)

  H)

  I)

  
• What type of tissue is the intralobular duct?

  • Simple cuboidal epithelium
• Intralobular Duct

  • Inta (inside); seen within  the lobules
  • Receive secretions from the intercalated discs
• Islet cells

  • Produces hormones that are secreted into the blood stream
  • Help control the level of glucose
• • Alpha cells
  • Produces glucagon
  • Raises glucose levels in the blood
• • Beta cells
  • Releases insulin
  • Lowers the glucose level
  • in type II diabetes, immune syst mistakenly destroys beta cells which stops production of insulin → pancreas loses ability to create insulin
• • Pancreatic acini
  • Acinus (latin) = Grape
  • Acinar cells
  • Form bundles that resemble grapes
  • Responsible for the synthesis, secretion, and storage of certain digestive enzymes

  Enzymes such as:

  • Amylase
  • Ligase 
  • Trypsin
• The function of alpha cells is to produce glucagon, while the function of beta cells is to release insulin.
• • Stomach 
  • Underneath the liver
  • First chemical site of digestion
• • Small intestine Parts
  • Duodenum
  • Ileum
  • Villi
• Small intestine

  • Duodenum - first straight
  • Ileum - curled portion
  • Mesentery 
  • Absorption of the digested nutrients occurs here
  • Villi
  • Folds
  • Carries absorbed nutrients away from the intestine
  • Holds the pancreas and stomach
• • Large intestine
  • Wider than the small intestine
  • Leads to cloaca
• • Cloaca
  • Sperm, eggs, shit passageway 
  • Terminates at the cloacal aperture
• • Anus
  • Opening 
• • Spleen 
  • Holding area of the blood
• • Kidney
  • Flat, bean-shaped organ 
  • Lower back of the frog near the spine
  • Dark in color
  • Filter waste from the blood
  • Top part of the kidney usually has fats 
• • Male parts
  • Testes 
  • Vestigial oviduct
  • No purpose
• • Female part
  • Ovary
  • Oviducts
  • Egg production here
• • Rugae
  • Folds of the stomach