DAT biology - Digestive System - IMPORTANT

Digestion

the breakdown of large pieces of food down into smaller pieces to prepare it for absorbtion

Intracellular digestion

unicellular organisms and some human cells digesting food via phagocytosis

phagocytosis

cellular intake and breakdown of food or foreign agents

With What do amoebas perform intracellular digestion

pseudopods

How do amoebas perform intracellular digestion

they utilize pseudopods to engulf food and trap it in a vescicle

Pseudopods

used by ameobas, they are temporary, finger like projections of the amoeba plasma membrane

What are pseudopods used for

cell movement and eating in ameobas

Extracellular digestion

digestion that occurs outside of individual cells

What does extracellular digestion use

Tissues, organs, and muscles

What are accessory organs of the digestive system

Gallbladder, liver, and pancreas

what are the two openings of the human digestive tract

the mouth and the anus

Mechanical digestion

The use of tissues, muscles and organs to physically break down food

Chemical digestion

the use of enzymes to chemically break down food

What digestion occurs in the mouth

Chemical and mechanical

What causes mechanical digestion in the mouth

Chewing

what causes chemical digestion in the mouth

salivary amylase

What does salivary amylase target

carbohydrates in the mouth, cause of chemical digestion in the mouth

What carbohyddrates does salivary amylase break down

starch into maltose

What are the main functions of saliva

contain salivary amylase and lubricates the food to form a bolus

What contains salivary amylase

saliva

What helps form the bolus

saliva

Bolus

mass of semidigested food

What is the larynx

The voicebox, food does NOT want to go here. It wants to go into the esophagus

what is the pharynx

a cavity that is common to both the digestive and respiratory system

What splits the pharynx into the esophagus and the trachea

the epiglottis

What is the esophagus

A muscular tube responsible for guiding food down to the stomach

What is the upper third of the esophagus made of

Skeletal muscle

What is the lower third of the esophagus made of

Smooth muscle

What is the middle third of the esophagus made of

skeletal muscle and smooth muscle

trachea

a cartilage reinforced tube responsible for guiding air into to lungs

What is the trachea reinforced by

cartilage

peristalsis

involuntary muscular function of the esophagus which allows it to guide food to the stomach

What kind of digestion is in the stomach

mechanical and chemical

What is the mechanical digestion in the stomach

churning of smooth muscle regions in the stomach

what is the chemical digestion that happens in the stomach

it occurs via Digestive Enzymes and acidic gastric juices

What kicks off the process of mechanical and chemical digestion in the stomach

distension

distension

outward stretching of the stomach, which is caused by the appearance of food into the stomach

cardiac sphincter

muscularized valve between the esophagus and stomach

what does the cardiac sphincter do

It is responsible for preventing backflow of food and gastric juices into the esophagus

Pyloric sphincter

a muscularized valve between the stomach and the small intestine

What is the pyloric sphincter responsible for

the deposit of chyme and gastric juice into the small intestine

Chyme

acidic, semi-digested food

Gastric pits

common indentations of the stomach lining which house multiple cell types

What triggers gastric pit cells

distension of the stomach

Gastric pits mnemonic

Mauricio’s good clinical practice

Mucous cells

G cells

Cheif cells

Pariteal cells

Mucous cells

Cell of the gastric pits that generates mucus

What does mucus cell lining do ?

It lubricates the stomach lining and protects it from low pH acids

G cells

cell in the gastric pit that secretes gastrin in response to distension

What does gastrin do

It is the trigger for parietal cells and cheif cells

what is gastrin released by

G cells in the stomach, part of gastric pits

Parietal cells

part of the gastric pits, release HIGHLY acidic gastric juice

What do parietal cells release

Highly acidic gastric juice

What is the gastric juice released by parietal cells composed of

Hydrochloric acid

What pH does gastric juice have

2

Cheif cells

cells in the gastric pits in the stomach that release gastric lipase and pepsinogen

What do cheif cells release

Gastric lipase and pesinogen

Gastric lipase

stomach enzyme that hydroyzes triglycerides

What is gastric lipase secreted by

chief cells, which work upon being stimulated by gastrin (secreted by G cells)

What does gastric lipase hydrolize

triglycerides

what is pepsinogen secreted by

chief cells, which work upon being stimulated by gastrin (secreted by G cells)

Zymogen

an innactive enzyme precursor

Pepsinogen

secreted by cheif cells, innactive form of pespin

Pesin

active form of pepsin, breaks down proteins in the stomach

What does pepsin break down

proteins in the stomach

How is pepsinogen activated into pepsin

via Hcl, activated via acids

What are the parts of the small intestine

The Duodenum

Jejunum

and the ileum

what % of digestion and nutrient absorption is the small intestine responsible for

90%

Mnemonic for parts of the small intestine

DJ EYE

Duodenum

jejunum

Eye - ileum

where does digestion occur

in the duodenum

where does absorption occur

in the jejunum and ileum

where are Goblet cells located

in the epithelium of the small intestine

what do goblet cells do

release a protective mucus that protects the small intestine epithelium

what do goblet cells protect from

they protect the small intestine epithelium from chyme

What does the small intestine release in response to chyme

CCK

What does the small intestine detect in order for it to release CCK

Proteins and fats

what does CCK do

it slows gastric emptying

stimulates the pancreas to release digestive enzymes

it stimulates the gallbladder to release bile

and it releases secretin

What does CCK do to gastric emptying rates

It slows them down

What does CCK do to the pancreas

It promotes the release of digestive enzymes

What does CCK do to the gallbladder

it promotes the release of bile

What does CCK do to the small intestine

It causes the release of secretin

What does secretin do

it stimulates the pancreas to release bicarbonate ion

what does bicarbonate ion do in the small intesitne

Chyme goes into the small intestine → small intestine produces CCK → CCK promotes the release of secretin → secretin causes the release of bicarbonate ion by the pancreas

It acts as a buffer

Pancreatic amylase

released by the pancreas to digest carbs (ie. starch into maltose)

What does pancreatic amylase do

released by the pancreas into the small intestine, it turns starch into maltose

Trypsinogen

released by the pancreas in response to CCK , zymogen of trypsin

Trypsin

formed from trypsinogen, protease released by pancreas

What does trypsin do

it turns chymotripsinogen into chymotripsin

What converts trypisnogen into trypsin

Enteropepsidase

Enteropepsidase

converts trypisnogen into trypsin

How is chemotrypsinogen turned into chemotrypsin

enteropepsidase turns trypsinogen into trypisin → trypsin turns chemotrypsinogen into chemotrypsin

What does the pancreas release in response to CCK

pancreatic amylase

Proteases: chemotrypsionegen and trypsinogen

What does the pancreas release in response to Secretin

HCO3-

What does bile do

emulsify fats

what does the liver do in terms of the digestive system

it produces bile

What does the gallbladder do

it stores and concentrates bile from the liver

What does the gallbladder do in response to CCK

it releases bile into the duodenum

Illeocecal sphincter

it connects the illeum of the small intestine to the cecum of the large intestine

how is food moved in the small intestine

via peristalsis

Enterocytes

cells of the small intestine epithelium

Crypts

invaginations in the intestival cell wall which contains cells that secrete enzymes and produce new intestinal lining epithelial cells