Ch 25: Digestive System Flashcards
What are the six functions of the digestive system?
Give a brief description of each.
- Ingestion: Taking in food through mouth
- Mechanical breakdown: In mouth and stomach
- Propulsion: Movement of food through the digestive tract via peristalsis
- Digestion: Chemical breakdown of food with enzymes all along the process
- Absorption: Taking in the chemical nutrients from food. Occurs mostly in the small intestines
- Defication: Removal of digestive waste via the anus
What are the two basic parts of the digestive system?
Briefly explain each.
- Alimentary canal: Pathway of food, from mouth to anus
- Accessory organs: Aid in digestion, but food does not pass through them
What are the two modes of digestive regulation?
- Extrinsic
- Intrinsic
What is extrinsic digestive regulation?
- Regulation that comes from outside the digestive system.
- Comes from brain and nervous system
- Specifically the PNS
What is intrinsic digestive regulation?
- Regulation that comes from inside the digestive system
- Occurs via gut hormones and the enteric nervous system via a group of nerves found in submucosa of plexus that provide for hunger feelings of the stomach
What are the anatomical parts of the alimentary canal?
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestines
- Large Intestines
What are the two accessory organs of the digestive system?
- Liver, including gall bladder
- Pancreas
Where is the esophageal sphincter and what is its purpose?
- It is located at the base of the esophagus where it meets the stomach.
- It closes to prevent backflow of stomach contents into the esophagus
- Prevents stomach acid from damaging esophageal tissues (acid reflux/heartburn)
Where is the pyloric sphincter, and what is its purpose?
- The pyloric sphincter is located at the exit point of the stomach where it meets the intestines.
- It controls the release of stomach contents to the duodenum
The process of taking in food from the mouth is called _____.
ingestion
The mechanical breakdown of food in the mouth uses what parts?
- Teeth
- Tongue
- Cheek muscles
The process of chewing is called _____.
mastication
Chemical digestion starts in the mouth with _____.
saliva
Saliva is exreted via _____.
salivary glands
Saliva consists of __% water, making it a _____ solution.
99%, hypotonic
Besides water, saliva also contains some _____, _____, _____, and _____.
acids, ions, amylase, antibiotic substances
*Amylase is an enzyme in _____ that breaks down _____.
saliva, starch
What are the antibiotic substances found in saliva and what purpose do they serve?
- Mucin
- Lysozyme
- IgA
- To kill microorganisms in food
Saliva is secreted constantly for _____ and _____.
cleanliness, moisture
The pharynx consists of…
- Hard palate
- Soft palate
- Nasopharynx
- Oropharynx
- Tonsils
- Laryngopharynx
The act of swallowing is called _____.
deglutition
What are the 3 phases of swallowing?
- Buccal/Oral
- Pharyngeal
- Esophageal
Describe the Buccal/Oral phase of swallowing.
- Voluntary
- Tongue and cheek muscles push food to back of mouth and down to laryngopharynx
Describe the pharyngeal phase of swallowing.
- Involuntary
- Soft palate blocks nasopharynx
- Tongue blocks entry to mouth
- Epiglottis blocks trachea
Describe the esophageal phase of swallowing.
- Food is pushed into espophagus
- Perstalsis takes it from there, moving bolus to the stomach
- Relaxation of the lower esophageal sphincter admits it into the stomach
What are the physical characteristics of the esophagus?
- Collapsed muscluar tube
- Mucosa consists of stratified squamous cells to protect from abrasion/acidic juices from the stomach
- Uses peristalsis to move bolus to stomach
The stomach is a _____, and its walls are _____.
storage sack, destendable
Define destendable.
The ability to expand due to internal pressure
Define rugae.
The folds of the enner walls in the stomach that allow it to be distended.
The first stomach sphincter of control is called the…
esophageal sphincter
The muscular layer of the stomach is called the _____.
muscular externa
The lining of the stomach is ….
discontinuous/incomplete
True or False
Stomach muscles contract via peristalsis
False
The irregular contraction of the stomach is called _____ and it is for _____.
churning, mechanical breakdown
What is the purpose of the alkaline mucus secreted in the stomach?
To protect the stomach from digestive acids
What are the two types of glands in the stomach lining?
- Gastric
- Pyloric
_____ stomach epithelium is closer to the esophagus, whereas _____ stomach epithelium is closer to the small intestines.
cardiac, pyloric
What are the five types of gland cells in the stomach lining?
- Mucus
- Regenerative
- Parietal
- Chief
- Enteroendocrine
What is the purpose of the mucus cells of the stomach?
To protect the lining of the stomach by excreting alkaline mucus to counteract stomach acids.
The regenerative cells of the stomach lining are…
stem cells that produce new epithelial cells
Parietal cells secrete _____, which _____ stomach pH.
Hydrochloric Acid (HCl), reduces
A normal stomach pH level is…
2.0
The addition of HCl to the stomach converts the bolus into _____.
chyme
*What orexigenic hormone is secreted by parietal cells and what is its purpose?
- Ghrelin
- Increases need to eat
*What two enzymes are secreted by chief cells?
Name functions.
- Lipase: breaks down lipids
- Pepsinogen: when released it is converted into pepsin by stomach acids and will breakdown proteins
Enteroendocrine cells secrete _____, which stimulates secretion of _____.
gastrin, hydrochloric acid (HCl)
Regulation of gastric secretions is through the _____ and _____ systems.
endocrine, nervous
What are the three phases of regulation of gastric secretions?
- Cephalon phase
- Gastric phase
- Intestinal phase
What are the characteristics of the Cephalon phase?
- Starts before food hits stomach
- Just the thought, sight or thought of food will start digestive system
- Sensory or mental input initiates HCl secretion nd enteroendocrine cells to stimulate gastrin
- Preps stomach for receipt of food
What are the characteristics of the Gastric phase?
- Food enters stomach
- Semi-digestion of proteins
- protein breakdown produces ammonia (NH3)
- NH3 increases pH and makes stomach more alkaline
- This stims gastrin production
- Gastrin initiates HCl, which decreases pH
- It is a negative feedback loop
- Too much HCl would inhibit gastrin
- Stres can also inhibit gastrin
What are the characteristics of the Intestinal phase?
- Food leaves stomach through pyloric sphincter
- Chyme slowly released into intestines
- Small intestines secrete intestinal gastrin
- Food is currently partially digested
- Enterogastric reflex
What are the characteristics of the enterogastric reflex?
- Found in small intestines
- Prevents too much food from leaving stomach
What are the two main functions of the small intestines?
- Complete digestion
- Absorption
What two accessory organs assist the small intestines with digestion?
- Liver
- Pancreas
Explain absroption in the small intestines.
When all food is broken down into its smallest components, they diffuse out of the small intestines into the capillaries
Explain the histology of the small intestines.
- Mucosa and submucosa folded into villi
- Simple columnar epithelia has a microvilli brushborder
- Villi and microvilli serve to increase surface area and increase diffusion
- Microvilli has enzymes that further breakdown disaccharides (sucrose and lactose)
What antibacterial juices are secreted in the small intestines?
- water
- mucin
- lysozyme
- T-cells
What do the alcholine secretions do in the small intestines?
neutralize chyme
Small intestines also contain MALT which is _____ and helps fight _____.
mucus associated lymphatic tissues, infection
_____ are collections of MALT in SI that monitor _____ and prevent the growth of _____ in the intestines.
intestinal bacteria populations, pathogenic bacteria
EXTRA CREDIT QUESTION
Relate urinary and digestive systems.
- The liver synthesizes the urea exreted by the kidneys
- This urea also contributes to the osmotic gradient that enables the kidneys to concentrate urine
- Intestines complement the kidneys in water and electrolyte reabsorption
TEST QUESTION
Describe the hepatic portal system of the digestive system.
- The two capilary beds of the hepatic portal system are located at the small intestines and the liver.
- Flow to small intestines:
- Aorta -> Superior mesentaric artery -> SI capillaries
- Purpose: supply blood to SI tract
- Flow to liver:
- small intestines -> Hepatic portal vein -> Liver
- Purpose: regulation of blood glucose levels and removal of any toxins
- Flow to heart: Liver-> Hepatic vein -> Inferior vena cava -> Heart
What is the blood flow to liver?
Aorta -> Celiac trunk -> Hepatic artery -> Liver
All blood from the SI goes through _____ before heading back to the heart.
the liver
What are the three main functions of the accessory organs?
State the organ of each.
- Bile production: Liver
- Regulation of blood glucose levels: Pancreas
- Removal of toxins: Liver
Bile is _____ that allows _____ to dissolve in H2O.
an emulsifier, lipids
Bile allows for the absorption of…
- fatty acids
- colesterol
- lipid based vitamins
Bile is produced by what type of cells?
hepatocytes
What is the flow of bile from hepatocyte to gall bladder?
hepatocyte -> bile canicul -> bile ductules -> hepatic ducts -> cystic ducts -> bile duct -> gall bladder
Regulation of blood glucose levels occurs through _____ and _____ that are secreted by the _____.
insulin, glucose, pancreas
Insulin _____ blood glucose levels by _____ cellular uptake.
lowers, increasing
Absorption of glucose _____ blood glucose levels.
reduces
_____ stimulates glycogen production.
Insulin
Glycogen takes _____ out of blood and stores it in the _____.
glucose, liver
Glucagon is a hormone formed in the _____ which promotes the breakdown of _____ to _____ in the liver.
glycogen, glucose
The breakown of glycogen _____ blood glucose levels.
raises
What organ is responsible for the removal of toxins?
Liver
What two secretions of the pancreas regulate blood glucose levels?
- insulin
- glucagon
Insulin and glucagon are _____ in that they are used to effect change (raise/lower) in blood _____ levels.
antagonistic, glucose
Pancreatic juices contain _____ that complete _____.
enzymes, digestion
What enzyme is secreted by the pancreas that is a base that neutralize chyme?
sodium bicarbonate (NaHCO3)
The pancreas secretes juices into the _____ which fuses with the _____.
pancreatic duct, bile duct
Bile and pancreas secretions are secreted into the _____ of the small intestines through the _____.
dodenum, hepatopancreatic sphincter
Define absorption as it pertains to the digestive process of the small intestines.
- All food is broken into its smallest components
- diffuses out of SI into capillaries
- Removes all nutrients
The large intestines are responsible for
the packaging of digestive wastes and H2O reabsorption.
What are the epithelial characterstics of the large intestines?
- mucosa not folded
- no enzymes
- goblet cells secrete mucus to lubricate fecal movement
What are the purpose of the bacterial flora of the large intestine?
- Help metabolize host molecules that can ferment undigested material
- Synthesize some vitamins (K, biotin)
The movement of material through the large intestines is by _____.
haustral contractions.
Describe haustral contractions.
- Movement is triggered through the distention of the hastral segments of the large intesteines
- One haustrum distends as it fills with chyme, which stimulates muscles to contract, pushing the contents to the next haustrum.
Defication is the removal of
solid wastes.
Chyme that has had its water content reabsorbed into the body is called.
Feces
Explain the process of defication from the end of the large intestine.
- fecal matter moves from large intestine into the rectum which contains stretch receptors letting the individual know its time to eliminate.
- stretch receptors cause defication reflex which causes contraction toward the external sphincter
- External sphincter is under voluntary control defication occurs under will of the individual.
