Chapter 24: The Digestive System Flashcards
(124 cards)
1
Q
What are the functions of the digestive system?
A
- ingestion
- mechanical processing
- digestion
- secretion
- absorption
- excretion
2
Q
Digestive System Function: Ingestion
A
- materials enter the digestive tract via the mouth (oral cavity
- the process of swallowing is called delutition
3
Q
Digestive System Function: Mechanical Processing
A
- crushing and shearing the ingested material to make it easier to propel along the digestive tract
- processes of chewing is called mastication
- increases the surface area allowing for enzymatic attack and subsequent breakdown of the material
4
Q
Digestive System Function: Digestion
A
- refers to the chemical breakdown of food into small organic fragments allowing for absorption by the digestive epithelium
- proteins, carbohydrates, lipids, nucleic acids must all be broken down to their monomers (building blocks) before it can be absorbed (done by digestive enzymes)
5
Q
Digestive System Function: Secretion
A
- release of water, acids, enzymes, buffers, salts by the epithelium of the digestive tract and by glandular organs
6
Q
Digestive System Function: Absorption
A
- movement of organic monomers, electrolytes, vitamins and water across the epithelium and into the interstitial fluid of the digestive tract
7
Q
Digestive System Function: Excretion
A
- removal of waste products from body fluids
- ejection of material as feces from the digestive tract is called defection or egestion
8
Q
The Digestive System is divided into 2 main groups:
A
- Digestive Tract Organs
2. Accessory Digestive Organs
9
Q
Digestive Tract Organs
A
- make up the Alimentary Canal (Gastrointestinal (GI) Tract)
- digestion and absorption
10
Q
Accessory Digestive Organs
A
assist in the process of digestion and absorption
11
Q
List the Digest Tract Organs
A
- Mouth (Oral Cavity)
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
- Anus
12
Q
List the Accessory Digestive Organs
A
- Salivary Glands
- Liver
- Gallbladder
- Pancreas
13
Q
Salivary Glands
A
secrete salivary amylase that begins carbohydrate digestion/breakdown
14
Q
Liver
A
a large metabolic organ that lies under the diaphragm and is made of 100,000 lobules
15
Q
Gallbladder
A
stores bile from liver and sends it to small intestine
16
Q
Functions of the Pancreas
A
- Exocrine produces pancreatic juice:
- Endocrine gland produces hormones that are released into the bloodstream after eating:
- insulin and glucagon
17
Q
Mouth (oral cavity)
A
- has 3 pairs of salivary glands
- stratified squamous epithelial tissue
- has tonsils at the back of the mouth and other lymphatic tissues important in fighting disease
- has teeth that begin mechanical breakdown of food (mastication)
- has tongue that tastes and pushes food for chewing and swallowing
18
Q
Pharynx
A
common passageway for solid foods, liquid and air
-material that is swallowed and enters the pharynx is now referred to as a bolus (mass of masticated material)
19
Q
Esophagus
A
- hollow muscular tube where peristalsis pushes food to stomach
- length is approximately 1 foot
- first third is skeletal muscle
20
Q
Stomach: Function
A
- stores food, starts digestion of proteins
- produces gastric juice that contains pepsin (an enzyme that breaks down protein)
- mechanical breakdown of the bolus liquefying it into a semi-liquid/solid paste called Chyme
21
Q
Small Intestine: Main functions
A
- mixes chyme with digestive enzymes for final breakdown
- absorbs nutrient molecules into body
- secretes digestive hormones into blood
22
Q
Large Intestine
A
also known as the large bowl ~5 feet
larger in diameter but shorter than the small intestines
23
Q
Rectum
A
Stores and regulates elimination of feces
24
Q
Pathway of Food
A
Mouth -> Pharynx -> Esophagus -> Stomach -> Small Intestines -> Large Intestines -> Rectum -> Anus
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4 Major Layers that Makeup the Wall of the Alimentary (GI) Tract
1. Mucosa (innermost layer)
2. Submucosa (second layer)
3. Muscularis Externa (third layer)
4. Serosa (outermost layer)
26
Mucosa layer
- produces mucus (line with mucous membranes) that protect lining
- simple columnar epithelial tissue
- involved in absorption (in certain regions of GI tract)
- also produces digestive enzymes and hormones (in certain regions of GI tract)
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Submucosa layer
layer of loose areolar connective tissue that contain blood vessels, lymphatic vessels and nerves
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Muscularis Externa layer
made of 2 layers of smooth muscle that move food along the GI tract (in the stomach, there are 3 layers)
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Serosa layer
part of the peritoneum
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Enteric Nervous System
- "brains of the gut"
- accounts for intrinsic control of digestion which consists of 2 major intrinsic nerve plexuses.
.. (add more later)
31
What are the two major intrinsic nerve plexuses?
1. Submucosal Nerve Plexus
| 2. Myenteric Nerve Plexus (lies between circular and longitudinal muscles of the muscularis externa)
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Tongue
covered in taste buds called Gustatory cells and assist in the mechanical breakdown and swallowing of food (deglutition) and moves it toward the pharynx
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What are the three pairs of salivary glands?
1. parotid (cheek area)
2. sublingual (under the tongue)
3. submandibular (jaw area)
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Saliva contains
- water, mucins (lubricant
- mucous
- lysozyme
- salivary amylase
- lingual lipase
- electrolytes
- IgA
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2 Types of Teeth
1. Primary Dentition (aka deciduous teeth or baby teeth) - 20 deciduous teeth
2. Secondary Dentition (aka permanent teeth or adult teeth) - 32 permanent teeth
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The Process of Swallowing
1. Voluntary Phase
| 2. Involuntary Phase
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Voluntary Phase of Swallowing
the beginning of food being swallowed from the mouth into the pharynx
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Involuntary Phase of Swallowing
- once the food is in the pharynx swallowing becomes a reflex.
- the epiglottis covers the glottis to make sure food is routed into the esophagus
- food moves down the esophagus through peristalsis
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Peristalsis
rhythmic contractions
40
Stomach: Structure
- thick-walled J-shaped organ that lies on the left side of the body beneath the diaphragm
- mucosa layer has deep folds called rugae and gastric pits that lead into gastric glands that secrete gastric juice
41
What are the three smooth muscle layers in the muscularis layer of the stomach?
1. Oblique (inner)
2. Circular (middle)
3. Longitudinal (outer)
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What are the 4 types of secreting cells?
1. Chief Cells
2. Parietal Cells
3. Enteroendocrine Cells (G cells)
4. Mucus Neck Cells
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Chief Cells
produce Pepsinogen (inactive enzyme that breaks down protein)
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Parietal Cells
- produces intrinsic factor (helps the absorption of Vitamin B12 in the small intestines)
- produces Hydrochloric Acid (HCl) which makes the stomach extremely acidic (pH of 2)
- This acidic condition activates Pepsinogen -> Pepsin (an active enzyme)
45
Enteroendocrine Cells (G Cells)
- produces Gastrin
| - other secretions: Histamine, Serotonin & Somatostatin
46
Mucus Neck Cells
produce mucus (thin, soluble)
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Small Intestines: Structure
- main site of absorption for the entire GI tract (90%) of absorption
- consists of cells called Brush Border cells (Absorptive Cells)
- smaller in diameter than the large intestines, but longer than the large intestines (~18-20 feet long)
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Brush Border cells (Absorptive cells)
absorb the organic building blocks and also has attached enzymes called brush border enzymes
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lactose
galactose + glucose
50
Sucrose
glucose + fructose
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Maltose
glucose + glucose
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Pancreas
an elongated, spongy organ found tucked behind the stomach (~6 inches)
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Products of Pancreatic Juice
- Digestive Enzymes: Carbohydrase, lipase, nucleases, and proteases.
- Bicarbonate ion
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Glucagon
hormone released when blood sugar falls
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Insulin
hormone released when blood sugar rises
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Carbohydrases
breaks down carbohydrates
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Lipase
breaks down lipids, fats
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Nucleases
breaks down DNA and RNA
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Proteases
breaks down proteins
60
Bicarbonate ion
helps neutralize stomach acids
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Metabolic Pathway
metabolic reactions (catabolic and anabolic) reactions involved in a series of steps
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What are the 6 functions of the liver?
1. filters blood from GI tract to remove poisons and detoxify the blood
2. breaks down hemoglobin
3. removes iron, vitamins A, D, E, D and B12 from blood and stores them
4. removes glucose as glycogen and breaks it down to help retain blood glucose levels
5. makes plasma proteins and helps regulate cholesterol levels by making bile salts
6. Produces Bile, while the Gallbladder stores bile
63
During the digestion process, the gallbladder
- will contract releasing the bile into the duodenum.
| - bile emulsifies the lipids and fats allowing further breakdown by lipases
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Hepatic Portal System
-substances (amino acids, monosaccharides, components of nucleotides but NOT including glycerol or fatty acids) that are absorbed in the small intestine are filtered through the liver via the hepatic portal system
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Absorption of lipids are absorb via the
lymphatic system. NOT the Hepatic Portal System.
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Hepatic Portal system Pathway
Hepatic Portal Venule -> Hepatic Portal Vein -> LIVER -> Hepatic Vein -> HEART -> Hepatic Artery
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5 Functions of the Large Intestines
1. re-absorption of water to prevent dehydration
2. absorption of vitamins (B complex and K) produced by the normal flora
3. compaction of the intestinal contents into feces and elimination through the anus
4. storage of feces
5. cecum has projection called the appendix that may play a role in fighting infections
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4 Divisions of the Large Intestines
1. Cecum (pouch-like)
2. Colon: ascending, transverse, descending, sigmoid
3. Rectum
4. Anal Canal
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deglution
process of swallowing.
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bolus
soft mass of chewed food
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chyme
the semifluid mass of partly digested food expelled by the stomach into the duodenum
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rugae
one of the folds of mucous membrane on the internal surface of the stomach
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cardia
the upper opening of the stomach, where the esophagus enters
74
fundus
- Located at the uppermost section of the stomach.
- Its function is to store accumulated gas, which is produced as a by product of digestion, and to store extra food as needed.
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pyloric sphincter
- band of smooth muscle at the junction between the pylorus of the stomach and the duodenum of the small intestine.
- acts as a valve to controls the flow of partially digested food from the stomach to the small intestine
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gastroesophageal sphincter
ring of smooth muscle fibers that allows food into the stomach from the esophagus, but prevents gastric juices and partially digested food (chyme) to regurgitate back into the esophagus
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pylorus
- the opening from the stomach into the duodenum (small intestine)
- prevent intestinal contents from reentering the stomach when the small intestine contracts and to limit the passage of large food particles or undigested material into the intestine
78
gastric juice
the digestive fluid, containing pepsin and other enzymes, secreted by the glands of the stomach
79
gastric pit
any of the numerous depressions in the mucous membrane lining the stomach into which the gastric glands discharge their secretions
80
enamel
- covers the pulp area filled with nerves and blood vessels
| - made of calcium salts and protects the tooth from wear and tear
81
dentin
calcified connective tissue that makes up a majority of the tooth
82
root canal
an extension of the pulp cavity that contains the nerves and blood vessels
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pulp cavity
contains pulp (connective tissue containing nerves and blood vessels)
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cementum
bone like substance that attaches the root to the periodontal ligament
85
What are the three divisions of the stomach?
1. fundus (superior portion)
2. body (main portion)
3. antrum/pylorus (inferior portion)
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plicae circularis
- deep, permanent folds of the mucosa and submucosa of the duodenum
- slows chime, increasing the amount of surface area available for the absorption of nutrients.
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villus/villi
- fingerlike projections of the mucosa of the small intestine
- increase surface area for absorption of nutrients
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microvilli
- make up the brush border of the small intestine
| - increase surface area for absorption of nutrients
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brush border enzymes
- (located in the microvilli) within the GIT (gastrointestinal tract)
- are involved in the terminal process of the digestion of carbohydrates and proteins.
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pancreatic juice
contains digestive enzymes and releases it into the duodenum of the small intestines
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Enzyme Formula
Enzyme (E) + Substrate (S) -> ES Complex -> E + Product (P)
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Optimum enzymatic action or function at
specific temperature and/or pH
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active site
egion of an enzyme where substrate molecules bind and undergo a chemical reaction
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catabolism
the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy
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anabolism
the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy
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hydrolysis
the chemical breakdown of a compound due to reaction with water
97
dehydration
chemical reaction that involves the loss of a water molecule from the reacting molecule
98
List the major enzymes that are used in carbohydrate digestion
1. salivary amylase
2. pancreatic amylase
3. maltase
4. lactase
99
List the major enzymes that are used in protein digestion
1. pepsin
2. trypsin
3. peptidases
100
List the major enzymes that are used in nucleic acid digestion
1. nuclease
| 2. nucleosidases
101
List the major enzymes that are used in fat digestion
1. lipase
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Salivary Amylase: Produced by? Site of Action? What does it digest?
Produced by salivary glands.
Site of Action: mouth
Digests: starch + H2O -> maltose
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Pancreatic Amylase: Produced by? Site of Action? What does it digest?
Produced by: pancreas
Site of Action: small intestine
Digests: starch + water -> maltose
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Maltase: Produced by? Site of Action? What does it digest?
Produced by: small intestine
Site of Action: small intestine
Digests: maltose + H2O -> glucose + glucose
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Lactase: Produced by? Site of Action? What does it digest?
Produced by: small intestine
Site of Action: small intestine
Digests: lactose + H2O -> glucose + galactose
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Pepsin: Produced by? Site of Action? What does it digest?
Produced by: gastric glands
Site of Action: stomach
Digests: Protein + H2O --> peptides
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Trypsin: Produced by? Site of Action? What does it digest?
Produced by: pancreas
Site of Action: small intestine
Digests: protein + H2O -> peptides
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Peptidases: Produced by? Site of Action? What does it digest?
Produced by: small intestine
Site of Action: small intestine
Digests: peptide + H2O --> amino acids
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Nuclease: Produced by? Site of Action? What does it digest?
Produced by: pancreas
Site of Action: small intestine
Digests: RNA and DNA + H2O --> nucleotides
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Nucleosidases: Produced by? Site of Action? What does it digest?
Produced by: small intestine
Site of Action: small intestine
Digests: nucleotides + H2O -> base + sugar + phosphate
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Lipase: Produced by? Site of Action? What does it digest?
Produced by: pancreas
Site of Action: small intestine
Digests: fat droplet + H2O -> monoglycerides + fatty acids
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emulsification
- The breakdown of fat globules in the duodenum into tiny droplets, which provides a larger surface area on which the enzyme pancreatic lipase can act to digest the fats into fatty acids and glycerol.
- assisted by bile
113
chylomicron
- a droplet of fat present in the blood or lymph after absorption from the small intestine
- transport dietary fats and cholesterol from intestines to tissues
114
List the steps in carbohydrate digestion
1. pancreatic amylase breaks down starch and glycogen into oligosaccharides and disaccharides
2. brush border enzymes break oligosaccharides and disaccharides into monosaccharides
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How are monosaccharides and amino acids absorbed?
3. monosaccharide/amino acids are con-transported across the apical membrane of the absorptive epithelial cell. (uses Na+ concentration gradient established by Na+ and -K+ ATPase pump in the basolateral membrane)
4. monosaccharide/amino acids exit across the basolateral membrane by facilitated division and enter the capillary via intercellular clefts
116
List the steps in protein digestion
1. pancreatic proteases break down proteins and protein fragments into smaller pieces and some individual amino acids
2. brush border enzymes break down protein fragments into amino acids
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List the steps in fat digestion
1. emusfication - bile salts in the duodenum break large fat globule into smaller fat droptlets
2. digestion - pancreatic lipases hydrolyze triglycerides, yielding monoglycerides and free fatty acids
3. micelle formation - micelles (consisting of fatty acids, monoglycerides and bile salts) ferry their contents to epithelial cells
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How are fatty acids and monoglycerides absorbed?
4. diffusion- fatty acids and monoglycerides diffuse from micelles into epithelial cells
5. chylomicron formation - fatty acids and monoglycerides are recombine and packed with other fatty substances and proteins to form chylomicrons
6. chlyomicrons are extruded from the epithelial cells by exocytosis, enter lacteals and are carried away from the intestine in lymph
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HDL (high-density lipoprotein)
well-behaved "good cholesterol." This friendly scavenger cruises the bloodstream. As it does, it removes harmful bad cholesterol from where it doesn't belong.
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LDL (low-density lipoprotein)
- the "bad" cholesterol that carries mostly fat and only a small amount of protein from the liver to other parts of the body
- It collects in the walls of your blood vessels, where it can cause blockages.
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VLDL (very low-density lipoprotein)
- contains very little protein
- main purpose of VLDL is to distribute the triglyceride produced by your liver.
- high VLDL cholesterol level can cause the buildup of cholesterol in your arteries and increases your risk of heart disease and stroke.
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Gastrin
a stomach hormone that stimulates Chief cells and Parietal cells and contraction of the muscularis
123
Histamine
stimulates parietal cells
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Serotonin & Somatostatin
both stimulate contraction
