Organismal Biology

Involves the degradation of large molecules in to smaller molecules that are absorbed directly by cells

• Utilize intracelular digestion
• surround and engulf food via phagocytosis and enclose food in vacuole 
• Lysosomes digest food and unusable exits in a vacuole

• Cillia sweep microscopic food into oral grove where food vacuole forms around food
• Enzymes enter vacuole and products diffuse into cytoplasm, solid waste exits vis anal pore

• Employ both intracellular and extracellular digestion
• Tentacles bring food into the mouth and release the particles into a cuplike sac (gastrovascular cavity)
• Endodermal cells lining the cavity secrete enzymes
• Thus digestion principally occurs outside th cells
• However, once in small particles the gastrodermal calls engulf the nutrients and digestion is completed internally
• Undigested food is expelled through the mouth

• Body is many cells thick: requires a more advanced digestion
• Allows for specialization for mechincal and chemical digestion and absorption of the food
• Parts include mouth, pharynx, esophagus, crop (stores food), gizard (grinds food), intestine (doral fold for increased surface area and absorption) and anus

Similar to annelida but with the addition of complex appendages and salivary glands

Involves the regulation of a physical parameter that maintains normal cell homeostasis via negative feedback loop

Control signals feed into certain cells and cause the measured parameter to change direction

• Mechanical and Chemical 
• Saliva digests carbs and lubricates food
• Stretch receptors in the stomach cause release of juices that are very acidic and breaks down H bonds and 3D structure 
• Stomach contents separete (lipids on tome, then proteins, then carbs)
• stomach pushes carbs and proteins first, easiest to derive E from
• Pancreatic fluids rich in Bicarbonate ions that neutralized stomach acids (in small intestine)
• Bile is secreted by liver to help absorb fat vis emulsification
• Smooth muscle of small intestine moves chyme down intestine
• Products are absorbed as they travel through small intestine

Partially digested food, enters small intestine

• Rich in Bicarbonate ions that neutralized stomach acids (in small intestine)
• Endocrine and exocrine
• Release bicarbonate to neutralize pH in small intestine
• Also secretes amylases, lipase, protease (breakdown proteins)

• Third part of small intestine
• All food is absorbed here
• Bile salts from liver are reabsorbed and recycled back to liver
• Unabsorbed material is excreted

• Chemical and mech digestion
• Salvia contains salivary amylase secreted from salivary glads starts digestion

• Is inactivated by low pH in stomach
• Amylase in center of food bolus can stay active longer (digests 50% of starch)

Food ball

Passageway from mouth to stomach

• Prevents air from entering GI system
• Band of muscle at top of esophagus

• Prevents food from backing up when chest pressure lowers (lungs inflate)
• Heart burn protection

• PH1-2
• Stores food as digested and absorbed
• Protein digestion starts here with low pH an enzyme pepson

• Inactive form of pepsin
• HCL in stomach activates pepsin
• Pepsin usually remains inactive because it shreds proteins and will shred the proteins that produce it 
• Mucous stops strong acids and protects stomach

• Duodenum First segment
• Jejunum second segment
• Ileum Third segment
• Lots of surface area

Regulates passageway of chyme into small intesting

• Hormone released by small intestine cells in duodenum
• Hormone stimulates release of amylase, lipase (fat digestion), bile (fatty acid emulsification) 
• Also stimulates contraction of pyloricn sphincter
• CCk controls negative feedback loop for fat breakdown, is released due to fat digestion products

• Hormone that stimulates the release of bicarbonate ions from pancreas if too much chyme enters the duodenum and one time
• Causes contraction of pyloric sphincter
• Faster cyhme movement, faster pH control chyme

• Stimulates the release of HCL and pepsinogen to further breakdown proteins and amino acid chains in stomach before enters duodenum
• Negative feedback look for protein breakdow gats released if stomach empties too fast, pyloric sphinter shuts 

• Secrete into intestine vs blood stream
• Pancreas is both

• Large circular folds the protrude into interior of intestine
• Made of epithelial cells that have microvilli which increase surface area
• Core of each villi lie a blood capillaries that drain villus into hepatic portal vein --> liver or further packaging and storage biomolecules

• Also known as colon
• Reabsorbed water and salts
• Bacteria here help digest other material that enzymes cannot breakdown
• ex: vitamin K and cellulose

• Are ampatipatic and will stabilize fat droplets in solution via emulsification allows for absorption of fats
• Secreted by liver stored in gull bladder
• Bile Pigments and salts act as emulsifies

• Differences in vertebrates are from dietary differences
• Involve shape of teeth
• Length alimentary canal (how long tract is)
• Presence of enlarged/multi-chambered stomach called ruminants

chambers of stomach