Digestive System Flashcards
six functions of the digestive system
- ingestion
- secretion
- propulsion
- digestion
- absorption
- defecation
organs of the alimentary canal
- oral cavity (mouth)
- pharynx
- stomach
- small intestine
- large intestine
accessory organs and structures involved in the digestive process
- teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
peritoneal membrane (or peritoneum, the serous membrane of the abdominopelvic cavity)
consists of two layers
- parietal peritoneum (outer)
- visceral peritoneum (inner)
- peritoneal cavity (between the layers)
intraperitoneal vs. retroperitoneal regions
intraperitoneal are located entirely within the peritoneal cavity
retroperitoneal are located partly or completely outside the cavity
2 prominent mesenteries of the abdominopelvic cavity
greater omentum and lesser omentum
4 layers that make up the wall of the GI tract
mucosa, submucosa, muscularis externa, and either the serosa or adventitia.
role of the mucosa layer
coats the epithelium, protecting it and the underlying tissues from ingested food and chemicals secreted by digestive organs. Houses regenerative epithelial cells that have a high rate of mitosis, allowing the mucosa to replace epithelial cells as they are damaged or sloughed off in the alimentary canal
nerve plexus in the submucosa layer
submucosal plexus
nerve plexus in the muscularis layer
myenteric plexus
sphincter
special, circular muscles that open and close certain body parts. Most often, the action of a sphincter is to regulate the passage of some type of fluid, such as bile, urine or fecal matter
relationship of smooth muscle contraction and the types of motility
in oral cavity, the pharynx, the superior portion of the esophagus, and the last portion of the large intestine, motility is due to skeletal muscle. In the rest of the alimentary canal, motility is the work of smooth muscle. Motility takes several forms (swallowing, churning, peristalsis, and defecation)
interaction of the sympathetic, parasympathetic and enteric nervous systems and their effects on mobility and secretions
Nervous system regulation of motility is accomplished by the nerves of the ANS. The sympathetic and parasympathetic branches of the ANS generally have opposite effects on gastrointestinal motility—sympathetic activity inhibits digestive processes, and parasympathetic activity stimulates them
Short reflexes from the ENS (local)
long vs. short reflexes and their regulation over the digestive process
short reflexes- reflex pathways are confined to local neurons
long reflexes- must travel outside the local digestive neurons to the CNS to function
3 hormones that participate in regulating digestion
gastrin ( stomach ), secretin ( small intestine ), cholecytokinin (small intestine), gastric inhibitory peptide (small intestine), and motilin (small intestine)
function of hard and soft palate
hard- assists in mechanical digestion
soft- prevent food from entering the nasal cavity
function of the intrinsic and extrinsic muscles of the tongue
intrinsic- control the shape and size of the tongue, push the food against the hard palate during chewing, which assists in mechanical digestion, and also push the bolus posteriorly during swallowing
extrinsic- control the position of the tongue, move the tongue during chewing and help turn the food into a bolus
function of the papilla on the tongue
filiform- assists in mechanical digestion
fungiform, circumvallate, foliate- taste buds
3 major salivary glands
- parotid
- submandibular
- sublingual
components of saliva
water, enzymes, mucus, salivary amylase, lysozyme, secretory IgA, bicarbonate ions, other solutes
functions of saliva
moistening, lubricating, cleansing the oral mucosa. deters growth of bacteria in the oral cavity, mechanical digestion, chemical digestion
roles of the sympathetic and parasympathetic nervous system in regulating saliva production
Sympathetic nerves innervate the salivary glands and their ducts, triggering increased saliva production and facilitating saliva transport through ducts
sympathetic- stimulate mostly mucous cells
parasympathetic- stimulate mostly serous
mastication
the process of chewing during which food is physically broken into smaller pieces by the teeth, tongue and hard palate
structure of the teeth
crown (visible portion), root (embedded), enamel (outer layer of hard mineralized substances), pulp(soft inner gelatinous substance), dentin (inner layer of mineralized tissue in both the root and crown)
region(s) of the pharynx where both food and air pass
oropharynx, esophagus
structure that prevents food from going up into the nose
uvula
structure that prevents food from entering the larynx
epiglottis
type of muscle found in the superior and inferior esophageal sphincters
superior- skeletal
inferior- smooth
deglutition
specialized type of propulsion that pushes a bolus of food from the oral cavity through the pharynx and esophagus to the stomach
peristaltic movement
Peristaltic waves move the bolus down the esophagus to the stomach
This phase begins as the upper esophageal sphincter relaxes. Neurons of the enteric nervous system then stimulate the inner circular and outer longitudinal layers of the muscularis externa to undergo peristalsis and “massage” the bolus inferiorly toward the stomach.
Figure 22.10 gross anatomy of the stomach
Review
function of the gastric folds
Rugae, allow the stomach to expand considerably
Figure 22.11 histology of the stomach wall
Review
Why the stomach has 3 layers of smooth muscle
additional layer of smooth muscle allows the stomach to perform churning, a motion that pummels the food into a liquid called chyme
cells that line the gastric pit
mucous neck cells, parietal cells, chief cells, diffuse neuroendocrine system cells
substances/hormones produced from the different cells of the gastric pit
mucous neck cells- secrete acidic mucus to mucus prevent the mucus from neutralizing the acid produced by other cells known as parietal cells
parietal cells- secrete HCl that activates pepsinogen, destroys most disease causing organisms we digest
cheif cells- pepsinogen (becomes pepsin in contact with acidic pH, begins protein digestion)
diffuse neuroendocrine cells- gastrin and histamine (stimulates acid secretion from parietal cells)
how the stomach protects itself from HCl
Between the gastric pits we find columnar epithelial cells that secrete a thick mucus layer that lines and protects the cells of the stomach from its own secretions
role of HCl
Acid is an important component of gastric juice because it is required to activate a precursor enzyme called pepsinogen (pep-SIN-oh-jen) and also because it destroys most disease-causing organisms we ingest
chyme
liquid mixture that results from the stomach churning a bolus and mixing it with gastric juice
3 phases that regulate digestion in the stomach and how they are initiated
- cephalic phase (sight, smell, taste or even thought of food)
- gastric phase (when food enters the stomach)
- intestinal phase (the presence of partially digested proteins in the fluid entering the duodenum)
3 functions of the stomach
secretion, propulsion, digestion
How might a stomach problem lead to pernicious anemia?
The most common cause of pernicious anemia is the loss of stomach cells that make intrinsic factor. Intrinsic factor helps the body absorb vitamin B12 in the intestine. The loss of parietal cells may be due to destruction by the body’s own immune system
Figure 22.14 Gross Anatomy of the small intestines, know function of each structure
Review
Figure 22.15
Review
villi
folds of the mucosa and submucosa of the small intestine that increase surface area for absorption
microvilli
highly folded extensions of the plasma membrane that increase its surface area for absorption
lacteal
a lymphatic capillary that absorbs dietary fats in the villi of the small intestine
brush border
Each enterocyte has as many as 3000 microvilli, which gives the cell the appearance of a bristle brush, or brush border, on microscopic examination. Associated with the brush border are numerous digestive enzymes produced and secreted by enterocytes, such as sucrase, maltase, and lactase, which catalyze reactions that break down disaccharides, and peptidases, which catalyze reactions that break down peptides.
goblet cells
secrete mucus
hormone CCK
causes gallbladder to contract and release bile, stimulates secretion of pancreatic enzymes from acinar cells, relaxes hepatopancreatic sphincter
hormone secretin
inhibits gastric motility and acid secretion, smilute bicarbonate ion release from pacreatic duct cells, increase bile production from the liver
segmental movement vs. peristalsis
segmental- involves contractions of only the circular layer of smooth muscle, which produces a squeezing motion, functions of segmentation are mechanical digestion and mixing the chyme with intestinal and pancreatic enzymes as well as bile
peristalsis- accomplished by alternating contractions of the longitudinal and circular layers of smooth muscle in the muscularis extern, function is to propel chyme toward the ileum and ultimately through the ileocecal valve to the cecum
enterogastric reflex
A nervous reflex whereby stretching of the wall of the duodenum results in inhibition of gastric motility and reduced rate of emptying of the stomach. It is a feedback mechanism to regulate the rate at which partially digested food (chyme) leaves the stomach and enters the small intestine
duodenum
where bile and pancreatic juice are secreted
receives partially digested food (known as chyme) from the stomach and plays a vital role in the chemical digestion of chyme in preparation for absorption in the small intestine
jejunum
most active site for chemical digestion and absorption
ileum
ileocecal valve- controls the movement of materials from the ileum into the cecum. This sphincter also prevents materials in the large intestine from flowing backward into the ileum. This function is key because, as we discuss shortly, the large intestine houses a great number of bacteria that could cause illness if they entered the ileum.
ileocecal valve
a sphincter muscle situated at the junction of the ileum (last portion of your small intestine) and the colon (first portion of your large intestine). Its function is to allow digested food materials to pass from the small intestine into your large intestine
Figure 22.17
Review
Figure 22.18
Review
substances which are typically absorbed across the wall of the large intestines
water and electrolytes
role of bacteria in the large intestine
produce vitamins, metabolize undigested materials, deter the growth of harmful bacteria, stimulate the immune system
metabolism
the sum of the body’s chemical reactions
catabolism
one in which a substance is broken down into smaller parts
anabolism
one in which smaller compounds are combined to make a larger compound
primary nutrients used to generate ATP
glucose, fatty acids, amino acids
oxidation v reduction
substance that loses electrons is oxidized, and the substance that gains electrons is reduced
glycolysis
a series of reactions that takes place in the cytosol during which glucose is split and small amounts of ATP and NADH are generated
What happens to pyruvate under anaerobic conditions?
it is reduced to lactate
Intermediate step
fate of pyruvate, either reduced to lactate or moves into mitochondria and is oxidized, to enter the citric acid cycle. Co-enzyme- A forms acetyl-coA
Citric acid cycle
2nd part of glucose metabolism, 8 reactions that take place in the mitochondrial matrix during which sugars are oxidized and AP and reduced electron carriers are generated
Electron transport chain
group of electron carriers in mitochondrial membrane through which electrons are passed as part of oxidative phosphorylation
Explain where each of the following molecules enters into the biochemical pathway of cellular respiration- glucose, glycerol and fatty acids, deaminated amino acids
glucose- glycolysis
glycerol- glycolysis
fatty acids- B-oxidation
deaminated amino acids- transamination
Glycogenesis
the storage of excess glucose taken in from the diet
Glycogenolysis
breakdown of glycogen to release glucose monomers into the blood
Gluconeogenesis
formation of new glucose from noncarbohydrate precursors
Glycolysis
the breakdown of glucose by enzymes, releasing energy and pyruvic acid
Lipogenesis
the process by which fatty acid and triglyceride synthesis occurs
Lipolysis
breakdown of fats and other lipids by hydrolysis to release fatty acids
Beta-oxidation
process by which fatty acid molecules are broken down to generate acetyl-coA
absorptive state
time period from the. point when ingested nutrients enter the bloodstream to about 4 hours after eating
general nutrient levels in the blood during the absorptive state
Oxidation of nutrients, primarily glucose, provides fuel to cells
Synthesis of amino acids into proteins provides structural materials to cells
Glycogenesis stores excess glucose in skeletal muscle cells and hepatocytes
Lipogenesis stores triglycerides in adipocytes and hepatocytes
the function of insulin on most cells, on the liver, on adipose tissue, and on muscle cells
stimulates the uptake of glucose by cells, lowering concentration of glucose in the blood
postabsorptive state
period of time from about 4 hours after feeding until the next meal
general nutrient levels in the blood during the postabsorptive state
Breakdown of proteins in muscle cells releases glucogenic amino acids into the blood
Ketogenesis in hepatocytes converts fatty acids to ketone bodies and releases them into the blood
describe functions of glucagon hormone on liver and adipose tissue
triggers glucogenolysis and gluconeogenesis
Which region of the nervous system regulates appetite and satiety?
satiety center
Which hormone suppresses appetite?
leptin
Which hormone promotes hunger?
ghrelin
metabolic rate
the total amount of energy expended by the body to power all its processes
How does exercise influence basal metabolic rate (BMR)?
increases above normal
variables that influence BMR
hormones, fever, nutritional status, physical activity, drugs
core body temperature
the temperature of deeper structures in the body such as the liver
why it is important to maintain core body temperature
significant disruptions in all body systems
center of control of body temperature
hyptothalamus
figure 23.18 how the nervous system regulates body temperature.
Review Figure
how the thyroid helps to maintain body temperature
increase the metabolic rate of their target cells, and heat production
risks of hypothermia and hyperthermia
hypo-decrease, slows down body’s enzymes, slows breathing and heart rate, frostbite
hyper-elevated, increase enzyme activity and the rate of the body’s reactions, produces more heat which leads to a positive feedback loop
macronutrients vs. micronutrients
macro- required in large amounts including carbohydrates, proteins, and lipids
micro- required in small amounts, vitamins and minerals
essential vs. non essential nutrients
essential- nurtient that cannot be manufactured by the body so must be obtained through diet
table 23.1 the three major types of macronutrients
Review Figure
figures 22.22 and 22.23
Review
What is the difference between monosaccharides, disaccharides, and polysaccharides with respect to their structure?
mono-one di-two -poly-many
What is the role of fiber?
Fiber plays a major role in digestive health. Fiber is the fuel the colon cells use to keep them healthy. Fiber also helps to keep the digestive tract flowing, lowering cholesterol
function of carbohydrates
They provide you with energy for daily tasks and are the primary fuel source for your brain’s high energy demands. Fiber is a special type of carb that helps promote good digestive health and may lower your risk of heart disease and diabetes
structure and function of triglyerides
Triglycerides consist of a glycerol “backbone” along with three fatty acids bonded to the backbone in an ester linkage, store fat for energy, insulation and protection
difference between unsaturated and saturated fatty acids
saturated- have hydrocarbon chains with no double bonds between carbon atoms
unsaturated- have hydrocarbon chains with one or more double bonds between carbon atoms
essential vs. non essential amino acids
essential-must be supplied by diet
non- can be synthesized from carbon skeletons
complete vs. incomplete proteins
complete- supplies all the essential amino acids
incomplete-lacks one or more
differences between fat soluble and water soluble vitamins and provide examples for each
fat-soluble- have a structure similar to that of cholesterol, with one or more hydrocarbon rings and long hydrocarbon chains. For this reason, they are nonpolar and are therefore hydrophobic and soluble in other lipids (A, D, E, K)
water soluble- have predominantly polar bonds and are therefore hydrophilic and soluble in water (B’s and C)
mineral
any element other than carbon, hydrogen, oxygen, and nitrogen that is required by living organisms
differences between major minerals and trace minerals
major- required in moderate amounts for optimal health: calcium ions, chloride, magnesium ions, phosphorus, potassium ions, sodium ions, and sulfur
trace- very small amounts necessary, including iodine, iron, selenium, and zinc
nitrogen balance
the difference between energy intake and expenditure
differences between positive and negative nitrogen balance
negative is bad
sources and functions of cholesterol
used as a precursor for many substances in the body including bile salts and steroid hormones
found in the diet in animal-based foods such as meats and dairy products
organ that produces cholesterol in the body
liver
relationship between dietary intake of cholesterol and the level of cholesterol synthesis in the liver
about 15% of the body’s cholesterol comes from the diet; the remaining 85% is made in the liver
