Digestive system lecture 18 A

Properties of the rugae

• Extensions that have various types of cells that secrete HCl/enzymes

• Also contain folding which increases surface area

Basics of stomach anatomy

• pH is 1-3

• Secretes a peptin enzyme that helps digest proteins

  • Proteins are more difficult to digest in comparison to other thingies

Basics of intestine anatomy

• There are folds!

  • Increasing surface area because we wanna maximize the extraction of carbs because we make a lot of ATP

• Folds are mostly made of villi

  • Highly vascularized because we’re taking in a lot of nutrients

• Peyers patch

  • Immune cells

• Myenteric Plexus

  • Contains NS cells

  • Remember: parasympathetic, rest and digest!

• pH is 7-9

• Bicarbonate!

• This is where most of digestion and nutrient absorption occurs

Microvilli / basic intestine anatomy cont

• Part of villi

• Increase SA even more

• Found on surface of enterocytes

  • they line the intestine

  • Often replaced!

  • Made in the crypt and move up as other ones kinda die off as we digest shit

  • These are how we can get away with eating bad things

• Endocrine cells on the bottom of the crypt that secrete hormones that regulate digestive tract

Small intestine - Duodenum

Proximal small intestine

• First 25 to 40 cm

• Has ligaments of treitz

  • Supports and anchors small intestine, made of skeletal/smooth muscle

• Contains a pocket shape where enzymes are secreted, bicarb, and overall majority of digestion occurs here

  • Ok guys basically bicarb is there to neutralize the acidic tummy acid

  • This is why the intestine is more basic than the stomach

• Digestion of polymers into dimers/trimers

Small intestine - jejunum

Mid small intestine

• The middle 250 cm

• Primary site of more digestion and absportion

• Digestions of Dimers, trimers into monomers

  • Once they’re monomers, they’re absorbed into enterocytes in apical side then sent to basal side of cells and out into blood stream

Small intestine - illeum

Distal small intestine

• Final 400 cm

• Rich in peyer’s patches

  • immune system upregulated here

• Reabsorption of bile salts

  • Important for fat digestion, vitamins, and other tingles

• Ileo-Cecal valves that help things only go in one direction

M-Cells

• In illum

• Line the epithelial layer of the digestive tract

• Gut associated lymphoid tissue (GALT)

• Taking in antigens and up regulate an immune response to them

Sections of large intestine

1. ascending colon

• runs up right side

• Includes cecum and appendix

• Note that appendix contains bacteria, or just pouches in general! Bacteria helps us by digesting things we can’t and essenciakky spitting the nutrients back to the intestine for us to absorb

2. Transverse colon

Runs under diaphragm

3. Descending colon

• Runs down left side

4. Sigmoid colon

• The final bend!

5. Rectum

Functions of large intestine

• Reabsorb water and beneficial things, such as electrolytes

• Primary site of microbial community and fermentation

  • Hypoxia environment, so makes sense that you have bacterias that are fermentators

• Whatever bacteria gives back (vitamins, AA) that’s beneficial gets reabsorbed here

Pancreas is endocrine and exocrine!

• Has ducts that are aligned with cells that secrete bicarbonate

  • Bicarbonate sent to ducts and then to the duodenum

  • example: like so when we eat a meal with lots of protein, HCl gets sent to te pocket thingy in the duodenum to digest, and so we have to neutralize the HCl with the bicarb

• Acinar cells

  • synthesizes digestive enzymes, sends them through the duct which is again connected to the duodenum

• Rememvber!!! digestion of polymers occurs in the duodenum

• islet cells release insulin and glucagon but this comes up later

Liver!! is the central distribution center

guys. listen very carefully: