A&P: Unit 3 study guide

What is the definition of digestion ?

process of breaking down food into nutrients for energy, growth, and cell repair

List in order from mouth to anus the path of food.

pharynx, esophogus, stomach, small intestine, large intestine, anus

When does the food become a bolus ?

in the oral cavity during chewing

When does food become chyme ?

in the stomach through mechanical churning

When does food become feces ?

in the large intestine between absorption and defecation

What digestive activities are happening in the mouth?

ingestion, mechanical breakdown, propulsion and digestion

What digestive activities are happening in the stomach?

mechanical breakdown

What digestive activities are happening in the small intestine?

mechanical breakdown, digestion, and absorption

What digestive activities are happening in the remaining GI tract?

propulsion (peristalsis)

What digestive activities are happening in the large intestine?

digestion, absorption, and defecation

Mechanical digestion

physically breaking down the size of food particles into smaller pieces without changing their chemical structure, ex: chewing and churning

Chemical digestion

enzyme driven process of breaking down large, complex, food molecules into small and absorbable nutrients through hydrolisis. Ex: saliva, pancreatic enzymes

What is peristalsis and where does it occur?

main method of propulsion in the adjacent segments of the GI tract as they contract and relax

What is segmentation ?

nonadjacent segments of the alimentary canal contract and relax to mix food and mechanically break it down by moving it foward and backwards in segments

What is the peritoneum ?

serous membrane that surrounds most abdominopelvic organs and the alimentary canal

Which later of the peritoneum lines the organs ?

visceral peritoneum

Which layer of the peritoneum lines the body wall ?

Parietal peritoneum

How does the peritoneum relate to the serosa layer of the alimentary canal?

contains serous fluid to lubricate the organs

What is peritonitis and how does a burst appendix cause it ?

inflammation of the peritoneum, bacteria from the gut in a burst appendix

What are the mesenteries and what are their main functions?

serous membanes that estend from forsal and ventral body walls to most abdomonopelvic organs and suspend some intraperitoneal digestive organs from the body wall

What is hepatic portal circulation?

drains nutrient-rich blood from the digestive organs and delivers it to the liver for processing

What are the four layers of the alimentary canal?

mucosa, submucosa, muscularis external, serosa

Mucosa

lines the lumen of the alimentary canal, secretes mucous digestive enzymes, and hormones

What cell types does the mucosa contain ?

connective tissue and smooth muscle

What digestive functions does the mucosa aid in ?

absorption of digestive end products and protects against infections due to the precense of MALT

In which layer is MALT found ?

Mucosa

Submucosa

consits of alveolar connective tissue that contains glands, blood and lymphatic vessels, lymphoid follicles and nerves

Muscularis externa

primarily smooth muscle responsible for peristalsis which moves food through the alimentary canal

What are sphincters in the muscularis externa/GI tract?

valves formed by the circular layer of muscularis externa

Serosa

visceral peritoneum that contains simple squamous epithelium and areolar connective tissue and the mesentary layer

1 mechanical stimuli that provides intrinsic control of the GI tract.

stretch

Name 3 chemical stimuli that provide intrinsic control of the GI tract

pH, nutrients, and solutes

Name 3 hormones that regulate GI tract activity.

Gastrin, CCK and secretin

Gastrin

released by stomach in response to food intake, targets cells in the stomach to secrete acid, small inestine to contract and large intestine to initiate defication

CCK

made in the duodenal mucosa and is stimulated by fatty chyme, targets the stomach to inhibit secretion from stomach and targets liver, gallbladder and pancreas to increase output of digestive juices

Secretin

msde in the duodenal mucosa and is stimulated by acidic chime, targets the stomahc to inhibit gastric gland secretion and targets the pancreas and liver to increase output

Which branch of the ANS stimulates digestion ?

parasympathetic fibers via vagus nerve

Which branch of the ANS inhibits digestive activities ?

sympathetic fibers

Short reflexes of the enteric nervous sytem.

intrinsic stimuli act within GI wall → stretch or changes in pH, nutrients, or solutes

Long reflexes of the enteric nervous sytem.

extrensic stimuli act through CNS

Which subdivisions of the nervous sytem provide inputs for long reflexes?

CNS

Whay digestive processes occur in the mouth and which accessory organs are necessary for these processes ?

ingestion, mechanical and chemical digestion by salivary glands, teeth and tongue

What is the lingual frenulum ?

anchors the tongue to the floor of the oral cavity

Which epithelial tissue type lines the mouth ?

stratified squamous epithelium to protect from abrasions

List the 3 salivary glands

pratoid, submandibular, sublingual

What is the function of saliva ?

dissolves food chemicals for taste, moistens and compacts food into bolus, beginds breakdown of starch w/enzymes

What are the components of saliva ?

water (electrolytes), enzymes (salivary amylase and lingual lipase), mucin, metabolic wastes, antimicrobials

How many baby teeth are there ?

20

Name the four classes of teeth

incissors, canines, premolars (bicuspids), molars

incisors

chisel shaped, cut

Canines

fanglike teeth, tear or pierce

Premolars (bicuspids)

broad crowns, rounded cusps, grind and crush

Molars

broad crowns, rounded cusps, best grinders

What are the three regions of the crown

crown, root, neck

Crown of a tooth

part above gingiva (gum), covered by enamel

root of tooth

portion embeded in jawbone

neck of tooth

connects crown to root

What are wisdom teeth ?

third molars

What is heartburn ?

when stomach acid regurgitates into esophogus

Which epithelial type lines the pharynx and esophogus ?

stratified squamous epithelium

What is chyme ?

acid slurry of ingested food formed in the stomach

What does the pyloric valve do ?

sphincter controlling stomach emptying

What digestive actions occur in the stomach ?

where the bolus of food becomes chyme, acid in the stomach pulverizes food

Can anything be absorbed in the stomach ?

yes

What are the cell types found in the gastric pits ?

Parietal, chief, enteroendocrine cells

What is secreted by parietal cells in the gastric pit ?

hydrochloric acid and intrinsic factor (required for vitamin B12 absorption)

What do chief cells secrete in the gastric pits ?

pepsinogen (inactive form of pepsin), and lipases (fat-digesting enzymes)

What is secreted by enteroendocrine cells in the gastric pit ?

paracrines and hormones (gastrin)

What is the function of gastrin ? In which organ?

stimulates secretion of HCl and hormones from the small intestine

Name the three phases of gastric activity.

cephalic phase, gastric phase, intestinal phase

Cephalic phase

CNS control, stomach responds to sensations or thoughts of food and emotional state

Gastric phase

intrinsic control, stomach distension, nutrient levels, gastric pH

Intestinal phase

intestinal control, stretching of duodenum, presence of nutrients in duodenum

what does salivary amylase breakdown ?

starch

What does lingual lipase breakdown ?

fats

Where is IgA found ?

secretions: sailiva, tears, breastmilk

when do wisdom teeth pop out ?

between the ages of 17-25

What causes sensitive teeth ?

when dentin is exposed without enamel

What type of cells line the mucosa ?

stratified squamous epithelium

place where the circular layer of the muscularis externa is thickened

sphincter

What does an exposure to acid do to cells ?

changes esophogeal cells → can turn into cancer

What is the intrinsic factor required for ?

B12 absorption

What are protease ?

enzymes that breakdown proteins (pepsin)

What is the autocatalytic affect ?

because pepsin breaks down proteins, and pepsinogen is a protein, pepsin is going to cleave pepsinogen to make more pepsin

What is hepatitis?

Inflamattion of the liver, causes include : viral infection, drug toxicity, wild mushroom poisoning

What is cirrhosis ?

progressive, chronic liver inflammation. Liver becomes fatty and fibrous. Causes include : chronic hepatitis, alcoholism

What digestive substance does the liver produce ?

bile

What type of molecule is broken down by bile ?

fats

Common hepatic duct

drains bile from liver

Cystic duct

drains bile from gallbladder

Bile duct

has a sphincter before it terminates in a portal into the small intestine

Where is bile stored and concentrated ?

gallbladder

What are gallstones ? Why do they form ?

crystalized cholesterole caused when there isnt enough biles salts or too much cholesterol, very painful

Does the gallbladder produce bile ?

No

Name the digestive enzymes found in pancreatic juice.

pancratic amylase and lipase, nucleases, trypsin, chymotrypsin, and carboxypeptidase

Why is the pH of pancreatic juice basic ?

to neutralize the acidic chyme that comes from the stomach

Proteases are produced by the pancreas in inactive forms. How does this help to protect the pancreas ?

it helps the pancreas not digest itself

Where are the proteases activated ?

duodenum

What are the 3 segments of the small intestine ?

duodenum, jejunum, ileum

Of the 3 segments of the small intestine, which does the most absorption ?

jejunum