Digestive Pt 1 thru slide 85 Flashcards
Refers to the use of the nutrients gained from food to
Build and maintain the structures of the body
Provide energy needed to keep us alive
Metabolism
Also refers to interactive set of chemical pathways that make life possible
Metabolism
Before food can be used for energy, growth and maintenance, and regulation of bodily functions, the nutrients have to be ______
Assimilated
when nutrient molecules enter cells and undergo many chemical changes
Assimilation
The act of breaking food molecules down into smaller molecular compounds that, in-turn, releases energy
Catabolism (a decomposition process)
The act of building nutrient molecules into large molecular compounds that requires the use of energy
Anabolism (a synthesis process)
Catabolism released energy in two forms:
- Thermal Energy (heat)
2. Chemical Energy
Released in frequent, small bursts or otherwise it would “cook” the cell it is being released in
____ energy is practically useless as an energy source for cells because it can’t be used to carry out work
This heat that gets released from all cells collectively maintains the body temperature for homeostasis
Thermal energy (heat)
Cannot be used directly for biological reactions
It first has to be transferred into the high-energy molecule of adenosine triphosphate (ATP)
Chemical Energy
The “universal biological currency”
Adenosine Triphosphate (ATP)
___ are readily absorbed in their original form:
Micronutrients
____ need to e small enough to be absorbed
Macronutrients
Micronutrients:
-28 considered essential
Do not provide calories of energy
Vitamins & Minerals
Macronutrients:
Proteins
Fats
Carbohydrates
Calories of energy per Macronutrient:
Protein 4 cals
Carbohydrate 4 cals
Lipids9 cals
Cheif energy source fo the brain
Glucose
Digestion of carbs requires ezymes called:
Amylases
Principle monosaccharide
Basic source of energy for cells
Found in things like fruits
Glucose
Principle monosaccharide (converted to glucose by liver)
Basic source of energy for cells
Found in things like fruits
Fructose
Principle monosaccharide (converted to glucose by liver) Found mostly in dairy products (milk, cheese, butter)
Galactose
Absorb-able form of carbohydrates:
Glucose
Fructose
Galactose
Byproduct of polysaccharide (starch) digestion
Found in excess in beer and some liquor (Barley)
Maltose
Glucose + Galactose
Principle sugar found in milk
Lactose
Glucose + Fructose
Ordinary table sugar
Sucrose
Disaccharides unable to be absorbed as is:
Sucrose
Lactose
Maltose
Polysaccharides unable to be absorbed as is or at all:
Starches
Glycogen
Cellulose (no absorbed or broken down)
Amylose and amylopectin combined
Potatoes, Corn, Oats, Rice
Starches
The stored form of glucose in the body
Found in the liver, muscle tissue, and some glial brain cells
Glycogen
Chemical name for fiber
Fruit skins, whole-grain rice (the husk is the fiber), legumes (the shell is the fiber), corn (skin on kernel is the fiber)
Cellulose
Carbohydrates can be classified in the diet as:
Simple
Complex
Monosaccharides and disaccharides
Fast source of energy
Can be found in fruits and milk, but also additives to things like candy, soda
This is why these can cause a quick burst of energy followed by a “crash” after because it is used so quickly
Simple Carbohydrate
More difficult to digest because of longer chain sizes
Polysaccharides
Provides a more consistent amount of energy while being broken down (if able to be broken down)
Can be found in things like whole grains, legumes, starchy vegetables
Complex Carbohydrates
Are most common form of lipid found in the diet and in the body
Triglycerides (TAGS)
Triglycerides are required for absorption of fat-soluble vitamins including:
A, D, E, K
Consists of one glycerol subunit that is attached to three fatty acids
A high-energy nutrient synthesized and stored in adipocytes (adipose cells) as well as hepatocytes (liver cells)
Triglycerides (TAGS)
Lipids
all hydrogen bonds are used (solid at room temp)
Found in animal meats and dairy fats
Can also be found in coconut and palm oils
Saturated Fatty Acids
1 glycerol cluster + 3 fatty acids =
Triglycerides or ‘fat’
not all hydrogen bonds are used (liquid at room temp)
Unsaturated
Olive, canola, peanut oils
Oils found in almonds, pecans, and avocados
Monounsaturated
Safflower, sunflower, soybean, corn oils
Polyunsaturated
Compound Lipids:
triglycerides combined with other components
Phospholipids
Glycolipids
Lipoproteins
Fatty acids + phosphorus + nitrogen
Lipid “bilayer” in cell membranes, part of the nerve sheath
Phospholipids
Fatty acids + carbohydrate + nitrogen
Part of cell membrane, helps to facilitate cellular recognition
Glycolipids
Chylomicrons
Very low-density lipoproteins (VLDL’s)
Low-density lipoproteins (LDL’s)
High-density lipoproteins (HDL’s)
Lipoproteins
Derived Lipids:
Steroids
Terpenes
Fat-soluble vitamins
Ketone bodies
In order to be absorbed at the cellular level, triglycerides have to be _____(broken down) into smaller components
- Fatty acids (FAs)
- Monoglycerides (MGs)
Hydrolyzed
Lipids need to be hydrolyzed by certain ___ enzymes
Lipase
(Cholesterol primary one)
Found in egg yolks, red meat, organ meats, shellfish, and dairy products
Steroids
Helps to build plasma membranes
Precursor in synthesis of Vitamin D
Requires for synthesis of androgens/sex hormones
Steroids
During _____ state blood may contain so many chylomicrons that it can appear turbid, or yellowish
Absorptive
In post-absorptive state (usually ~4 hours after meal) few ______ exist in blood
Contents have moved mostly into adipose tissue
Cholymicrons (lipoprotein)
Entering blood from adipose tissue or other cells, fatty acids combine with ____ to form FFAs
When rate of fat-catabolism increases (i.e. starvation), FFAs levels in blood increase markedly
Albumin
Lipoproteins:
Largest to smallest
Low protein to High
Least dense to most
slide #33
Chylomicrons VLDL IDL LDL HDL
Delivers triglycerides to cells throughout the body
Synthesized in enterocytes (intestinal cells) from fat and cholesterol absorbed in the small intestine
Very triglyceride-rich
Very large particle
Chylomicrons
Because of large size, have to enter lacteals (lymphatic capillaries) which carries them to thoracic duct to be dumped into blood
Chylomicrons
Delivers triglycerides to cells throughout the body
Very triglyceride rich
Large particle, smaller than chylomicron
Very Low-Density Lipoprotein (VLDL)
Synthesized in the liver from excess fats and cholesterol that have made it there from portal circulation
Very Low-Density Lipoproteins (VLDL)
Delivers cholesterol to cells throughout the body
As VLDL’s are stripped of their triglycerides, the “leftovers” get remodeled in the liver to form LDL’s
Smaller particles than VLDL’s
Low-Density Lipoproteins (LDL)
Reverse cholesterol transport for excess cholesterol
Returns excess cholesterol to the liver for recycling
Is made in both the liver and the small intestines
High-Density Lipoproteins (HDL)
Triglycerides are first hydrolyzed to yield fatty acids and a glycerol
Fatty acids are broken down into two carbon pieces (acetyl-CoA) by a process called ___-____
These then enter the citric acid cycle
Beta-oxidation
Glycerol is then converted to glyceraldehyde-3-phosphate which is then either:
Converted to glucose OR
Enters the glycolysis pathway
Synthesis of various types of lipids: Triglycerides Phospholipids Cholesterol Prostaglandins
AKA Lipogensis (Anabolism)
‘Building blocks’ of all cells
Proteins
Involved in the synthesis of certain neurotransmitters and hormones
Serotonin, epinephrine, melatonin, histamine
Protein
Absorption of proteins requires them to be broken down into any of the following:
- Amino Acid
- Dipeptide
- Tripeptide
Anything larger than (#) amino acids together is too large for absorption therefore requiring something to break it down smaller
3
Proteins are broken down by _____
Proteases
Of the 20 Amino acids, how many are essential, conditionally, and non-essential:
9 essential
7 conditionally
4 non-essential
Constitutes the major process for growth, reproduction, tissue repair, and replacement of all cells destroyed by wear and tear
Protein metabolism
anabolism & catabolism
Food is our only source of ____ energy
Most food particles are too large to be used by cells in their original form
Chemical
GI tract also known as:
Alimentary (nourishment) canal
Gastrointestinal tract (GI tract)
Approximately (##-##) feet long in living human
In a state of ____(sustained contraction)
Approximately (##-##) feet long in cadaver
-Variation is due to loss of muscular tone after death
16-23 feet
Tonus
23-39 feet
Accessory digestive organs:
Teeth Tongue Salivary glands Liver Gallbladder Pancrease
Term: Liquids into the mouth
Ingestion
Everyday, cells within the GI tract and accessory organs secrete ~## L of water, acid, buffers, enzymes into lumen of tract
7 Liters
Alternating contraction/relaxation of smooth muscle in walls of tract mix food and secretions and propel towards anus
Mixing and propulsion
Term: mix and movement of material along tract
Motility
Six basic process of digestive system:
- Ingestion
- Secretion
- Mixing & Propulsion
- Digestion
- Absorption
- Defecation
2 Forms of Digestion:
Mechanical
Chemical
Teeth cut and grind food before swallowed, smooth muscles of stomach and small intestine churn food- this helps to mix with enzymes to dissolve food
Mechanical Digestion
Large carbohydrate, lipid, protein, molecules are split into smaller molecules by hydrolysis- enzymes produced by salivary glands, tongue, stomach, pancreas, small intestine catalyze these catabolic reactions
Chemical Digestion
A few substances can be absorbed without chemical digestion, these include:
Vitamins
Ions
Essential Fatty Acids
Water
Entrance of ingested and secreted fluids, ions, and products of digestion into the epithelial cells lining the GI tract
These substances pass into blood or lymph and circulate to various locations in the body
Absorption
Wastes, indigestible substances, bacteria, cells sloughed from lining of tract, digested materials not absorbed leave the body through the anus
Defecation
Wall of GI tract from lower esophagus to anal canal has same basic four-layered arrangement of tissue
From outer layer to inner-most layer (contact with tract contents):
- Serosa or adventitia (depends on the location)
- Muscularis
- Submucosa
- Mucosa
Found on almost all parts of the GI tract
Serous membrane composed of areolar connective tissue and simple squamous epithelium (mesothelium)
Serosa
Also called the visceral peritoneum
Forms from a portion of the visceral peritoneum
Serosa
Single layer of connective tissue for the esophagus and proximal duodenum
Adventitia
Layers in Mouth, pharynx, superior aspect of esophagus
Also present in external anal sphincter, permits voluntary control of defecation
Muscularis - Skeletal (voluntary)
Found in the rest of the tract
Involuntary contractions help break down food, mix it with secretions, and propel it forward
Inner sheet of circular fibers, outer sheet of longitudinal fibers
Muscularis - Smooth (involuntary)
Network of neurons between the circular and longitudinal muscle layers
Myenteric Plexus (plexus of Auerbach) in Muscluaris
Consists of areolar connective tissue that binds the mucosa to muscularis
Contains many blood and lymph vessels that receive absorbed food molecules
Submucosa
Contains submucosal plexus (plexus of Meissner)
Extensive network of neurons
Submucosa
Inner lining of GI tract composed of 3 layers:
Mucosa
- Muscularis mucosae (outer)
- Lamina propria (middle)
- Epithelium (inner)
Thin layer of smooth muscle fibers
This layer is what causes the mucous membrane of the small intestine and stomach to have the folded appearance
These folds increase surface area for digestion and absorption
Movement of this layer ensures all absorptive cells are fully exposed to contents of GI tract
Muscularis Mucosae (outer Mucosa)
Areolar connective tissue containing many blood and lymphatic vessels which allow nutrients to reach other tissues of the body
Supports the epithelium and binds to the muscularis mucosae
Contains majority of mucosa-associated lymphatic tissue (MALT)
Lamina Propria (middle Mucosa)
This lymphatic nodular tissue contains immune cells that protect against disease
____ tissue present along GI tract especially tonsils, small intestine, appendix, and large intestine
Mucosa-Associated Lymphatic Tissue (MALT)
every 5-7 days these cells are replaced by new cells, old slough off and are excreted
Epithelium (inner Mucosa)
Nonkeratinized stratified squamous found in mouth, pharynx, esophagus and anal canal
Protective function
Epithelium (inner Mucosa)
Simple columnar found in ___ and ___
Secretion and absorption function
Tight junctions between cells here prevent leakage
Stomach and Intestines
Epithelium (inner Mucosa)
Secrete mucous/fluid/enzymes into lumen
Exocrine cells
Secrete hormones into lumen
Enteroendocrine cells
Considered the ‘brain’ of the gut:
Enteric Nervous System
Enteric nervous system arranged in two plexuses:
Both plexuses consist of neurons, interneurons, and sensory neurons
- Myenteric (Auerbach)
2. Submucosal Plexus (Plexus of Meissner)
Plexus located between longitudinal and circular smooth muscle layers of the muscularis
Myenteric (Auerbach)
Plexus found within the submucosa
Submucosal (Meissner)
Supply motor impulses to longitudinal and circular smooth muscle layers of muscularis
This leads to this plexus controlling the majority of GI tract motility
Particularly the frequency and strength of contraction of muscularis
Myenteric (Auerbach)
Motor neurons supply the secretory cells of the mucosal epithelium
This leads to this plexus controlling secretions of the organs of the GI tract
Submucosal (Meissner)
Connect the myenteric and submucosal plexuses (ENS)
Interneurons
Sensory Neurons- supply the ___ ___
Some function as chemoreceptors
Activated by certain chemicals in food located in the lumen of GI organs
Others function as baroreceptors (stretch receptors)
Activated when food stretches distends the wall of a GI organ
Mucosal Epithelium
Sympathetic nerve endings secrete _____ activating andrenergic receptors, stimulating cardia activity, yet inhibiting gastrointestinal activity
Nor-epinephrine
Vagus nerve endings secrete _____ activating cholinergic receptors, inhibiting cardiac activity, yet stimulating gastrointestinal activity
Acetylcholine (ACh)
Stimulation of the _____ nerves that innervate the GI tract causes an increase in GI secretion and motility by increasing activity of the ENS
Parasympathetic
Stimulation of the _____ nerves connected to the GI tract cause a decrease in GI secretion and motility by inhibiting the ENS neurons
Emotions such as fear (fight or flight), anger, anxiety may slow digestion because they stimulate the sympathetic nerves that supply the GI tract
Sympathetic
Largest serous membrane in the body:
Peritoneum
Peritoneum divided into:
Parietal
Visceral
Lines the wall of the abdominopelvic cavity
Parietal
Covers some of the organs and cavity and is also considered serosa
Visceral
Space between the two layers that contains lubricating serous fluid (small amount)
Peritoneal Cavity
Space that is behind the peritoneum
Organs in this space are anteriorly covered by the peritoneum:
Retroperitoneal:
- Kidneys
- Ascending colon (large intestine)
- Descending colon (large intestine)
- Duodenum (small intestine)
- Pancreas
Contains large folds that weave between the viscera
These bind organs together and then also to abdominal walls
Contain blood vessels, lymph vessels, and nerves that supply the abdominal organs
Peritoneum
Five major peritoneal folds:
- The greater omentum
- Falciform ligament
- Lesser omentum
- Mesentery
- Mesocolon
Largest peritoneal fold:
The Greater Omentum
Drapes over transverse colon and small intestine
Attaches to portions of stomach and duodenum, extending downward, anterior to small intestines, folds and extends upwards to attach to transverse colon
Contains considerable amount of adipose tissue which can expand with weight gain
Characteristic “beer belly”
Many lymph nodes here contribute macrophages and antibody-producing cells that combat GI tract infections
The Greater Omentum
Peritoneal “fold” that attaches the liver to the ventral surface (anterior) of the abdominal wall
Falciform Ligament
Free border of this ligament contains the ligamentum teres (aka round ligament; remnant of the umbilical vein)
Falciform Ligament
The ____ is the only digestive organ attached to anterior abdominal wall
Liver
lesser omentum
slides show
triglycerides combined with other components
Compound Lipids
Types of compound lipids
Phospholipids
Glycolipids
Lipoproteins
Food is our only source of chemical energy
Most food particles are too large to be used by cells in their original form
True or False?
True!
-Consists of all of the organs involved in the breakdown of food
- This system is a tubular system
- –Extends from the mouth to the anus
- –Forms extensive surface area in contact with the external environment
- –Closely associated with cardiovascular system because of the blood vessels involved in the digestive process
Digestive system
Cardiovascular… connection to digestive system?
Supplies digestive organs with O2 and processes nutrients
Endocrine
… connection to digestive system?
Hormones help regulate multiple actions in digestive system
Integumentary
… connection to digestive system?
Protects digestive organs; Helps with vitamin D for calcium absorption
Lymphatic
… connection to digestive system?
MALT defends against pathogens; lacteals absorb lipids to be transported into blood stream
Nervous
… connection to digestive system?
Sensory/motor neurons help regulate secretions and muscle contractions of GI tract
Respiratory
… connection to digestive system?
Provides oxygen and waste removal of CO2
Urinary
… connection to digestive system?
Kidneys make calcitriol which aids in calcium absorption in the GI system
Urinary
… connection to digestive system?
Kidneys make calcitriol which aids in calcium absorption in the GI system
Continuous tube extending from mouth to anus
—-Travels through thoracic cavity, through abdominopelvic cavity
Gastrointestinal tract (GI tract)
Gastrointestinal tract (GI tract)
consists of?
Mouth, most of pharynx, esophagus, stomach, small intestine, large intestine (and anus)
Accessory digestive organs?
Teeth
Tongue
Salivary Glands, liver, gallbladder, pancreas
Returning parasympathetic impulses stimulate salivation, returned along the fibers of both the _ and _ nerves
Facial (VII) nerve
Glossopharyngeal (IX) nerve
