Digestive System Basics & GI Tract Anatomy

What is the digestive system and what does it obtain

the organ system that allows us to process food, digest the nutrients, and remove waste
it obtains energy for atp production and raw material for building and repair

what is the 6 stages of digestion

ingestion, propulsion, digestion, absorption, compaction, and defecation

Ingestion

intaking the food

Propulsion

swallowing & peristalsis (muscle contractions that push food foward)

Digestion

mechanical and chemical breakdown of food to usable material

Absorption

uptake of nutrients/ nutrients enter body

compaction

absorbing water and consolidate indigestible material → basically removing water and compacting into feces

Defecation

removal of feces

What are the two types of digestions

mechanical and chemical

Mechanical digestion and why

The physical breakdown of food into smaller pieces - chewing/ churning through stomach and intestines → smaller pieces = more surface area exposed to digestive enzymes (doesnt change molecules = bread is still bread just small bits)

Chemical digestion

digestive enzymes → hydrolysis reactions that turn macromolecules into monomers

Chemical digestion turns polysaccharides, proteins, fats, and nucleic acid into what

polysaccharides → monosaccharides

proteins → amino acids

fats → monoglycerides and fatty acid

nucleic acid → nucleotides

What nutrients are usable without chemical digestion (5)

vitamin, amino acid, water, cholesterol, minerals

What are the two subdivision/ group of organs in the digestive system

Digestive tract (alimentary canal) and the accesory organs

Digestive tract / alimentary canal (7 organs)

the tube from mouth to anus that the food travels through

mouth → pharynx → esophogus → stomach → small intestine → large intestine → anus

GI tract (6)

Gastrointestinal tract thats part of alimentary canal/ digestive tract

Accessory organs

helps with the digestion but food doesn’t move through here

teeth, tongue, salivary gland, liver, gallblander, pancreas

Difference between digestive tract/ aliment canal and the GI tract

GI tract is only stomach and intestines
while digestive tract is from mouth to anus (mouth → pharynx→ esophagus → stomach → intestines → anus)

Peritoneum

Double layer of serous membrane tha surrounds the organs of the abdominal cavity

Mesentery and omentum (lesser and greater)

Mesentery - double layer of peritoneum that holds digestive organs in place to abdominal wall + carries their vessels and nerves

Omentum - a fold of peritoneum for the stomach → greater → from stomach and covers intestines → lesser → connecst stomach to liver

what are the 4 layers / tunics of the alimentary canal from innermost to outermost

mucosa, submucosa, muscularis externa, serosa

Mucosa

innermost layer of the alimentary canal

Epithelium → lamina propria → muscularis mucosae

also has MALT (mucosa associated lymphatic tissue)

Submucosa

connective tissue layer that contains vessels, nerves, and lymphatics

Musclaris externa - what is it and what 2 functions

2 layers of smooth muscle (inner circular, outer longitudinal) for peristalsis (pushing forward) and segmentation (mixing)

Serosa

outermost layer of the alimentary canal (digestive tract)

anchors the digestive tract to surrounding tissue

adventitia

replaces serosa in esophagus and rectum area

Enteric plexus -what is it and what does it regulate (3)

nervous network within digestive tract that regulates motility secretion and blood flow

What are the two neuron networks of the enteric plexus

submucosal plexus and myenteric plexus

How is motility and secretion of the digestive tract controlled (3)

neural control, hormonal control, paracrine secretions

What are the two neural controls of secretion and motility of the digestive system

Short myenteric reflex and long vagovagal reflex

Short myenteric reflex

reflex through the enteric/ myenteric plexus that reacts to stretch or chemical stimulation INSIDE the digestive tract

Long vagovagal reflex

reflex from parasympathetic stimulation /CNS

Hormone vs paracrine secretion

Hormones are released and travels to target elsewhere through bloodstream while paracrine secretion is when a cell release chemicals that affect nearby cells

gastrin, secretin

two hormones that regulate secretion and motility in the digestive tract