Digestive System Overview

My Digestive System Notes

Link to my Quizlet with all the terms.

Answers to prompts:

-Innermost layer, secretes mucus for the lubrication of movement and protection of the mucosa.

Epithelium: Non-keratinized stratified squamous epithelium at the start and finish, and non-ciliated simple columnar epithelium in the middle (throughout most of the length).

-Acts as a barrier to the lumen, facilitates secretion of digestive chemicals, and aids in absorption.

Lamina Propria: Areolar connective tissue, nerves, lymphatic vessels, site of MALT. Supports epithelial lining.

Muscularis Mucosae: Thin smooth muscle, its contractions move the mucosal lining to help with structural changes, gives shape to the mucosa.

-Dense irregular connective tissue in the middle of the wall (which means it has strength in all directions), it houses blood vessels, nerves and lymphatic vessels.

-Two layers of smooth muscle

-Circular layer (inner layer): Cells encircle tube

-Longitudinal layer (outer layer): Cells are perpendicular to the circular layer, run the length of the tube

-Added layer in the stomach, helps with peristalsis and segmentation

-Serosa: Located in peritoneal cavity, mesothelium and has a basement membrane of areolar CT. Secretes serous fluid to lubricate with the movement of the GI tract.

-Adventitia: Located outside the peritoneal cavity, dense irregular CT, holds the tube together, glues the tube in place in the surrounding tissue.

-Combo of Serosa and Adventita: Behind the peritoneal cavity (retroperitoneal) ex: duodenum + rectum

-One side is adventitia and the other side is serosa.

(Lumen is the hollow center)

-Oral Cavity: Has tongue for mixing stuff around and taste, as well as teeth for mechanical breakdown of food, and salivary glands for producing saliva that helps with chemical digestion + mucus for lubrication of food. Lined with non-keratinized startified squamous epithelium.

-Pharynx: Shared by digestive and respiratory and digestive system, directs food and air to different places. It has an epiglottis that forms a lid over the larynx to prevent choking and direct food to the esophagus. Lined w/ non-keratinized stratified squamous epithelium, also has mucus secreting cells for lubrication.

-Esophagus: Delivers bolus that we swallow to the stomach. Transitions in pharynx from non-keratinized stratified squamous epithelium to a non-ciliated simple columnar epithelium low in esophagus, folded back and forth for increased surface area. Muscularis externa transitions from skeletal muscle to smooth muscle for proplusion, the outer wrapping is adventita. Also has an esophageal hiatus where it passes through the diaphragm and connects with the stomach.

-Stomach: Mechanical breakdown and chemical digestion and stores food.

Cardiac sphincter: vomitting

Pyloric sphincter: Holds contents of stomach back, regulates how much can go into the duodenum.

Rugae: Temporary ridges of of mucosa that increase surface area and allow for expansion.

Muscularis Externa: Longitudinal and circular layers + oblique layers for churning. 

Outer wrapping: Visceral peritoneum; secretes serous fluid into peritoneal cavity.

Stomach has gastric pits that produce gastric juice. Gastric pits has many different specialized cells inside that contribute to overall function. 

-Small Intestine: Finish most of chemical digestion; major site of nutrient absorption in the body.

Digestive enzymes are produced outside the small intestine and delivered from the pancreas

Intestinal crypts: house stem cells that regenerate the lining.

Circular folds, villi, and microvilli: Maximize surface area for absorption.

-Large Intestine: Absorbs water and compacts and stores feces; defecation.

-Cecum, colon, and rectum.

-Microvilli to help with water absorption.

-Surrounds the anus (where feces exit the body).

-MALT is here.

-Liver: Store glucose as glycogen and release it to regulate blood sugar, process nutrients (lipids, amino acids) from the small intestine and release them into the bloodstream, store vitamins and minerals, produce plasma proteins, create bile to help digest fats (bile duct).

-Gallbladder: Stores and concentrates bile until it’s released into the small intestine (duodenum).

-Pancreas: Endocrine (hormones into blood), Alpha & Beta cells for blood sugar regulation. Exocrine: (digestive enzymes into small intestine).

Digestive enzymes in pancreatic juice:

Proteases: Break down proteins.

Amylase: Breaks down starch.

Sucrase and similar enzymes: Break down sugars.

Lipase: Breaks down fats.

Nucleases: Break down DNA/RNA.

Sodium bicarbonate: Neutralizes stomach acid.



*Image and helpful video below.