bio 12: digestive system

digestive system - mouth, stomach, liver, small intestine, pancreas, large intestine,

ingestion meaning

intake of food by mouth

propulsion meaning

movement of food by peristalsis; “wave like” muscle contractions that move food through digestive tract

digestion meaning

mechanical breakdown of food into smaller pieces

absorption meaning

passage of digested nutrients from gut into blood or lymph to distribute throughout body

defecation meaning

removal of indigestible waste from body

where does absorption take place

small intestine

what are lymphs

wbc’s that attack bacteria in blood or body tissue

proteins >

(sugar) carbohydrates >

fat >

nucleic acids >

peptides

glucose

fatty acids and glycerol

nucleotides

what is the gut

a tube that runs from mouth to anus

where does digestion happen first

mouth

what is the pH of the mouth

pH 7

what does the mouth start to digest

starch

what is the hard palate and the soft palate of the mouth consist of

hard palate: roof of mouth; several bones

soft palate: tonsils, uvula; muscle tissue

what do tonsils do

stop germs from entering body thru mouth or nose

how many teeth does a normal adult mouth have

32

what are the different teeth types

8 incisors for biting

4 canines for tearing

8 flat premolars for grinding

12 molars for crushing

what are the three sets of salivary glands that produce saliva?

name location, and what it contains

parotid - below ears, contains serious acini and makes watery saliva

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sublingual - below tongue, contains serious acini and mucous

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submandibular - below lower jaw, contains serious acini and mucous

what does saliva contain

water, mucus, and a salivary amylase which is a hydrolytic enzyme that breaks down STARCH in the presence of water

why is mucus important

lubricant to keep tissues (or other) from dying out

what does starch get broken into

maltose then glucose

whats a bolus

when food is chewed up

steps of what happens when swallowing

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(3)

1. soft palette moves back to cover nose opening
2. trachea moves up under a flap called EPIGLOTTIS, blocking its opening
3. opening to larynx (voice box) is called the GLOTTIS and is covered when trachea moves up by EPIGLOTTIS as well

what is the epiglottis

a flap of tissue that seals off the windpipe

review time!

what is the esophagus

a long tube that goes from pharynx to stomach

what is the pharynx also called

the throat

where is the pharynx located in between

mouth and esophagus

how does food move through the esophagus

thru peristalsis

what are sphincters

muscles that encircles tubes; open when relaxed and closed when contracted/tense

what is the cardiac sphincter

a valve between esophagus and stomach; where bolus reaches

structure and location of stomach

its thick and J-shaped, and is on the left side of the body beneath the diaphragm

how many layers of muscle does the stomach have and what does it do

3 layers and it contracts to churn and mix the contents of a bolus

how much solid/liquid can a stomach take

2 liters

what is the rugae and what does it do and why is it important

folds in stomach lining

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it increases the SA of the stomach; more SA allows greater intake of food and efficient absorption

what is the pyloric sphincter

a valve between the stomach and small intestine

what does the mucus lining of the stomach contain

contains inner gastric glands which produce GASTRIC JUICE that contains HCl and pepsinogen.

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when both combine it becomes PEPSIN which is a hydrolytic enzyme that breaks down proteins into peptides

whys the HCl in the stomach important

HCl gives the stomach a pH of 3 which helps kill bacteria in food and breaks food down

what is the inner wall of the stomach protected by

a thick layer of mucus secreted by mucosal cells

what happens when HCl penetrates the stomach

pepsin starts to digest the STOMACH LINING which forms an ulcer

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too much GASTRIC JUICE can cause ulcers (and too much stress as well)

what are ulcers and what can cure it

open sores in stomach lining

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from bacterial infections that impair the ability of cells to produce mucus and it can be cured by antibiotics

what is acid chyme and where does the stomach empty first

when the food gets turned into semi-liquid food after 2-6 hours

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the stomach empties into the first part of the small intestine called the duodenum and is controlled by the PYLORIC SPHINCTER

what makes the small intestine stay basic

sodium bicarbonate /NaHCO3 from the pancreatic juice makes the small intestine basic as it enters the duodenum

small intestine function

absorbs nutrients and some water from food

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chemical digestion

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propulsion and breakdown of chyme

what are the three parts of the small intestine

duodenum - connects to stomach

jejunum - middle of small intestine

ileum - connects to colon

how long is the duodenum

around the first 25 cm of the small intestine

how long is the small intestine

6 meters

what does the duodenum do

secretions sent from liver and pancreas break down fat and peptides and secretions from duodenum itself break down nutrients

where in the small intestine does most of the absorption of nutrients and vitamins

ileum

what do the walls of the S.I. consist of

interstitial glands that produce juices containing enzymes that FINISH the digestion of protein and starch

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peptidases digest peptides > amino acids

maltase digests maltose > glucose

whats the structure of the small intestine like

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3 points

long with complex walls to increase SA

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SA is further increased by finger-like projections called villi and interstitial glands are at the base of each villus

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villi are lined with columnar cells coated with microvilli and each villus contains blood and lymph vessels (lacteal)

what do villi do

it absorbs fat and increases SA

where is villi

small intestine

where in the small intestine does absorption take place in

across the wall of each villus

absorption; where do they go and how do they go?

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1. fatty acids and glycerol

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2. sugar and amino acids

hint: epithelial, lymphatic, capillary

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how is the hepatic portal vein created

1. absorbed across the villi and combined into fat molecules in the EPITHELIAL cells of the villus then move into the lacteal of each villus and enter the LYMPHATIC system

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2. enter the blood through capillary network

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its created by the merging of blood vessels from the villi

what do the blood vessels from the villi in the S.I. merge?

the hepatic portal vein which leads to the liver

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(blood vessel that carries blood from liver to intestines, pancreas, etc.)

what do the pancreas do

creates juice/enzymes to break down food

what is the location and structure of the pancreas

located behind the stomach and it is near the liver and gallbladder. the head of the pancreas lie in the curve of the duodenum and the body and tail are covered by the stomach

what juice does the pancreas make and what does it contain and do

it makes pancreatic juice; sends it into the DUODENUM through the pancreatic duct

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juice contains hydrolytic enzymes and NaHCO3 which makes the juice highly alkaline (basic) pH 8. it neutralizes the acid thyme and makes pH basic in the S.I.

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enzymes include pancreatic amylase (starch > maltose), trypsin (protein > peptides), lipase (fat droplets > glycerol + fatty acids)

what does lacteal take

fats

what is a duct

a tube or passageway

what does an exocrine and endocrine function mean

exocrine: makes substances like juice or saliva and releases it thru a duct

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endocrine: makes and releases hormones

what hormones do pancreas produce

insulin and glucagon

what do the two hormones that pancreas produce do

insulin - lowers blood glucose concentration and is produced by beta cells

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glucagon - raises blood glucose concentrations and is produced by alpha cells

steps if you’re hyperglycemic

1. beta cells of the pancreas release insulin into the blood

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2. some of the insulin goes to the liver and the liver takes up glucose (insulin) and stores it as glycogen

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3. other insulins goes into body cells; body cells take up more glucose

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4. blood glucose level declines to set point

steps if you’re hypoglycemic

1. alpha cells of the pancreas release into the blood

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2. glucagon is introduced and the liver breaks down glycogen and releases glucose to the blood

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3. blood glucose level rises to set point

how does diabetes occur

people who dont produce enough insulin or lack insulin receptors on target cells

liver structure and location

located above the stomach and in the upper right spot in the abdominal area. consists of 2 main lobes (large right and small left) that are both made up of 8 segments that have 1000 small lobes called LOBULES

liver functions

1. keeps blood concentrations of nutrients, hormones, etc constant (e.g. converts glucose > glycogen then back to glucose)

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2. interconversions of nutrients (e.g. carbo to fat, A.A to carbo or fats)

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3. detoxification from blood (by converting toxins to a water-soluble form so it can be removed as urine)

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4. production of bile

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5. destroys old RBC’s

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6. production of urea (breakdown of protein)

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7. manufacture of plasma proteins (e.g. albumin) which maintains intravascular volume

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8. manufacture of cholesterol

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9. storage or iron and vitamins

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10. in embryos, the liver makes RBC’s

what happens if bile is reduces

bile breaks down cholesterol and fat so if its removed or reduced, cholesterol cannot be broken down equals higher cholesterol

what is bile

a thick green liquid (green from byproducts of hemoglobin) and is a digestive fluid

what organ produces bile and where is bile stored

produced by the liver and stored in the gallbladder

bile function

carries away waste in the form of digestive fluid

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smaller parts of bile called bile salts break fat into fat droplets and SA is increased

* an increase in SA allows lipase to break fat further

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breaks down fat and turns it into energy

how does bile go to liver > gallbladder

thru a duct called common bile duct which sends bile to the duodenum

what is trypsin? where is it and what does it do

an enzyme that helps digest proteins

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found in the small intestine

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created by pancrea

what does amylase do

break down carbohydrates

is the pH of large intestine acidic or basic

basic

is the pH of small intestine acidic or basic

basic

what does the stomach break down

proteins into peptides

if the liver wasnt working how would that affect the villi

it would affect the absorption of fats

components of intestinal juice

hormones, digestive enzymes, mucus, and neutralizing substances released from the glands from both intestines

what does intestinal juice do and where is it produced

neutralizes HCl in the stomach

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releases hormones in the bloodstream

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has digestive enzymes that help with absorption

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the pancreas produce it

where is glycogen produced and stored

liver

where is lipase created and released

pancreas to duodenum

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through pancreatic duct

what is a reactant in the chemical digestion of food

water

where is starch digested

mouth and small intestine (from pancreatic enzymes)

where are peptides produced

pancreas, stomach, small intestine

what is jaundice

a condition that gives a person yellow skin

how is yellow skin caused (from jaundice)

due to the build up of BILIRUBIN in blood

what is bilirubin

breakdown of RBC’s

what is the cause of bilirubin

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what happens if u have it

when the body breaks down too many RBC’s too fast

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liver damage or blockage of bile duct

what are gallstones made out of

cholesterol and CaCO3

what can gallstones do to the body

can block bile ducts

what is the cause of viral hepatitis

jaundice AND liver damage

what is type A hepatitis

infectious; caused by unsanitary food

what is type b hepatitis

serum; spread thru blood contact like transfusions

what is cirrhosis caused by

an over consumption of alcohol

what happens to the liver if you drink too much alcohol over time

liver fills up with FAT DEPOSITS and SCAR TISSUE

what does alcohol break down into

lots of fatty acids

what are the 3 main functions of the large intestine

breaks down some indigestible food

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produces vitamins like B and K (e.g. convert food into energy AND makes proteins for bone building and blood clotting)

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abosrbs water and salt to make food dehydrated

what does feces consist of (5)

dead bacteria, indigestible material, inorganic substances, bile pigments, cell debris