Digestive System Flashcards
Alimentary Canal
Continuous muscular tube
Open on both ends
Begins in the oral cavity and ends at the anus
Composed of the mouth (oral cavity), pharynx, esophagus, stomach, small intestine, large intestine, anus
Accessory Digestive Organs
tongue, teeth, salivary glands, liver, pancreas, gallbladder
Four layers found in the alimentary canal
Mucosa (Innermost layer)- secretes mucus into the interior of the small and large intestine.
Submucosa (second inner layer) -contains blood and lymph vessels, lymph nodes, nerves, and mucus glands
Muscularis externa (third layer) -made of two layers longitudinal fibers and circumfrential fibers that help contract and move food.
serosa (outermost layer) -made of cells that make serous fluid
Lingual frenulum
vertical mucus membrane by which the body of the tongue is attached to the floor of the mouth.
Mouth is made up of what structures:
Lips- form the opening
Tongue -form the floor
Cheeks- form the walls
Hard and soft palete- form the roof
Uvula- form the posterior border
Uvula
hangs inferiorly from the soft palete
Tongue attachments
The mandible, hyoid bone, and lingual frenulum
Mastication
Mechanically food is chewed by the teeth in the mouth
Amylase
the salivary glands release this enzyme to chemically begin breaking down starches.
Salivary glands
Secrete saliva and amylase to moisten food and to begin breaking down starches
Maxilla
upper arch of teeth are located in the maxilla
Mandible
lower arch of teeth contained in the mandible
How many teeth and what kind?
32 teeth total
4 types of teeth that accommodate a meat and vegetable diet.
One half of each jaw has:
2 incisors for biting
1 canine for tearing
2 premolars for grinding
three molars for crushing
Three parts of the tooth
The crown, neck, and root
Root of tooth
The largest part of the tooth located within the alveolar process of the jaw bone
Neck of tooth
located within the upper portion of the gums
Crown of tooth
located above the gum (the part you can see
Pulp Cavity
At the center of every tooth there is a pulp cavity that has blood vessels and nerves (that allow for sensations of heat, cold, and pain
Dentin
bone like substance composing most of each tooth
Enamel
Hardest substace in the body- made of connective tissue, that protects the crown of the tooth
Tongue
grips and repositions the food in between the teeth to form a bolus (mass of compact food)
papillae
raised bumps on tongue
3 types: fungiform, circumvallate, and filiform
Taste buds are on fungiform and circumvallate papillae
Pharynx
nasopharynx, oropharynx, laryngopharynx
Two layers of muscle (circumferential outer layer and inner longitudinal layer) – contract alternatively causing peristalsis to squeeze food into the esophagus
Stomach anatomy
c-shaped organ
concave lesser curvature and convex greater curvature
Peritoneum
stomach is covered by serous membrane called greater omentum and lesser omentum
Lesser omentum
peritoneum that attaches the lesser curvature of the stomach to the liver
Greater omentum
hangs down like an apron and attaches the greater curvature of the stomach to the posterior wall of the abdomen, covering the transverse colon, and the anterior surface of the small intestine
Rugae
folds within the stomach that allow it to expand and hold more food (2-4 liters)
Stomach has two purposes –
hold food and to mechanically mix food with gastric juices by vigorously contracting when food is present
the stomach has three muscular layers - longitudinal layer, circular layer, and a special oblique layer that help breakdown the food into smaller pieces for later stages of absorption (chyme- soupy consistency of the stomach contents)
Ulcer
a sore caused by disintegration of tissues (can be caused by h.pylori - which leads to duodenal ulcers by eating away at the mucosal lining
Three parts of the small intestine and the valve that allows chyme to enter from the stomach
The pyloric sphincter is the valve that controls the opening of the small intestine - only allowing a small amount of chyme to enter at time
Duodenum, jejunum, ileum (slightly longer than the jejunum)
ileocecal valve
The valve that controls entrance into the large intestine from the small intestine.
pyloric sphincter
controls the entrance of the small intestine.
The duodenum
This is the shortest part of the small intestine, and the point of entry for the pancreatic and liver enzymes (bile) enter the small intestine.
What three things increase absorption in the small intestine
circular folds, villi, and microvilli all increase surface area promoting greater absorption of nutrients.
** These increase the 20 foot long small intestine to 1800 square feet
** the small intestine is specialized in absorption
Small intestine and absorption
Carbohydrates and proteins are only partially digested when they enter the small intestine so the samll intestine carry out digestive functions.
Absorption cells are all along the surface of each villus (villi multiple)
Each villus has blood vessels and a lymphatic vessel called LACTEAL
How are sugars and amino acids absorbed in the small intestine
The enter the villi and absorbed by capillary beds present in the villi.
Nutrients are carried to the hepatic portal circulation (of the liver) before entering general blood circulation
How are larger molecules (glycerols and fatty acids) absorbed in the small intestine
These are too large to be carried by the capillaries.
They are transported into lacteals (ex. fatty acids get reconfigured into triglycerides) and eventually enter the general blood circulation through a thoracic duct
Epithelial cells of villi
produce intestinal enzymes that remain attached to the microvilli and plasma membrane and complete digestion of peptides and sugars
Internal sphincter (anus)
Involuntary
External Sphincter (anus)
Voluntary
Hepatic flexure
Turn of large intestine (90 degrees by the liver)
Splenic flexure
Turn of large intestine (90 degrees on patient left)
Cecum
Start of the large intestine controlled by the ileocecal sphincter
Large intestine functions
bacteria (good) secrete vitamins (k and b) which are absorbed – as they breakdown the chyme they release vitamins.
water absorption - water is absorbed and stool is formed
Compaction of waste
Defication- through the anus
Pancreas
The pancreas sends pancreatic juice into the duodenum via pancreatic duct. It contains sodium bicarbonate that neutralizes the chyme (high pH from the stomach acid)
Has digestive enzymes that act on every component of food.
Pancreatic enzymes
Pancreatic amylase - digests starch to maltose
trypsin- digests proteins to peptides
lipase - digests fat droplets in glycerol and fatty acids
** Enzymes travel via pancreatic duct to the hepatopancreatic ampulla into the duodenum of the small intestine
Liver function in digestion
Makes bile that is stored in the gallbladder where it is stored before entering the small intestine
Emulsifies fat into fat droplets that can mix with water
Bile is sent to the duodenum via common bile duct
Stores glucose as glycogen and breaks it up in between meals so maintain glucose levels
Makes urea from excess amino acids that are that are removed from excess amino groups
Why is bile green
it contains pigments from hemoglobin
Stomach digestion
mechanical and chemical
When food (bolus enters) - hormone gastrin stimulates gastric juices (pepsiogens, mucus, and hydrochloric acid) generating high pH to kill bacteria and to break up food
Pepsinogen
pro-enzyme secreted by chief cells of stomach.
Hydrochloric acid turns it into pepsin which starts the breakdown of proteins
Mucus in the stomach
protects the stomach from hydrochloric acid and pepsinogens
Parietal cells
secrete Hydrochloric acid
Peptides
result from first step of protein digestion are digested by peptidases in amino acids
Maltose
the result from first step of starch digestion is digested into glucose by maltase
Chloecystokinin
chyme stimulates the small intestine to release two hormones - secretin which causes the liver to release bile, and chloecystokinin which causes the gallbladder to secrete chloecystokinin
Both of these hormones stimulate the pancrease to release its juices
secretin
causes the liver to release bile
Bile
bile contains bile salts that emulsify fats
hypothalamus
plays a role in hunger and satiety
if it is damaged then a person may not be able to regulate the hunger/satiety balance properly
Hormones that increase hunger
Ghrelin, endorphins, neuropeptide-y
Hormones that decrease hunger
Leptin, serotonin, and Chloecystokinin
lipids
saturated, unsaturated, and cholesterol
complete proteins
contain all 9 amino acids needed - animal protein, eggs, dairy products, and soybeans
incomplete proteins
do not contain all, but some of the amino acids needed - grains, seeds, nuts, legumes
vitamins
organic compounds that are not consumed in metabolic reactions, but help enzymes carry out the metabolic processes
water soluble and fat soluble
minerals
inorganic compounds not consumed in metabolic reactions but also help enzymes facilitate metabolic reactions
cellular respiration
the process that generate ATP
Glycolysis
takes one glucose molecule and make two pyruvate
Krebs cycle
happens in the mitochondria and is the central pathway for respiration - NADH, FADH2, ATP
Electron transport chain
NADH, FADH2 carry high energy electron through a series of electron acceptors, causing H+ ions to be pumped out the membrane -causing a strong differential across mitochondrial space
proton motive force
strong differential across mitochondrial space causes H+ ions to flow through ATP synthase producing 34 ATP
lipid metabolism
occurs in the liver in times of slow energy needs - produces twice as much ATP then carbs or protein
Protein metabolism
only happens when carbs or fats are not available – produces ammonia during protein metabolism that needs to be combined with CO2 to make urea and excreted from the body
Proteins are the building blocks for cells, so its best not to use them for ATP production
Peritstalsis
The squeezing of food through the GI tract by alternating contractions of the longitudinal and circumferential muscles.
Feces content
75 percent water 25% solid matter containing intestinal bacteria, undigested plant material, fats, bile pigments, inorganic material, mucus, dead intestinal cells
4 roles of the digestive system
ingestion, digestion (mechanical and chemical), absorption, and dedication
How does leptin work?
It is produced by adipose cells. The role of leptin is to alert the brain to turn off the hunger center in the brain and activate the satiety center when consuming a meal.
How does Ghrelin work?
Ghrelin is produced by the stomach and travels to the brain to stimulate the hunger center and deactivate the satiety center
What are the major biochemical substances we need
Carbs, proteins, and lipids in large amounts. Vitamins, and minerals in small quantities.
cellular respiration
during cellular respiration , glucose combines with oxygen to produce ATP, CO2,
cellular respiration
the process of making ATP
Aerobic respiration
uses Oxygen, and releases CO2, H2O, and ATP
carbs
main source of energy for cells - provided by glucose metabolism
glucose is a major metabolic pathway used for ATP production (can yield up to 38 in aerobic cellular respiration
glycolysis yields 2 ATP and 2 pyruvate
pyruvate yield 2 more ATP
Central pathway for cellular respiration is?
Citric acid Cycle (TCA cycle)
The pyruvate is coverted to 2 more ATP, and CO2 byproduct and NADH, FADH2 these will carrier electrons to the ETC -where the Most ATP will be made.
ETC
NADH and FADH2 carry electrons to terminal electron acceptors
The energy is captured in the inner membrane space of the mitochondria
The electrons are carried through a chain of electron acceptors causing H+ to be pumped out
the strong differential causes a proton motive force that causes H+ to diffuse through ATP synthase and producing 34 ATP
what digestive functions are carried out by the small intestine
Digestion and absorption
enzymes are released by the pancreas to continue digestion of starches and proteins
Digestion of fat begins
Digestion is almost complete at the end of the small intestine and ABSORPTION is almost complete also with absorption of sugars and amino acids
