Test 4 Material Flashcards
Gastrointestinal System
Organs that collectively perform digestion and absorption
Digestion
Breaking down of food into molecules small enough to be absorbed
Absorbtion
Passage of molecules through plasma membranes of cells lining stomach and intestines into blood and lymph
Structures of the Gastrointestinal System
1) Gastrointestinal Tract
2) Accessory Digestive Organs
Gastrointestinal Tract
-a.k.a. alimentary canal
-Continuous tube from the mouth to to anus
Accessory Digestive Organs
-Teeth
-Tongue
-Salivary Glands
-Liver
-Gallbladder
-Pancrease
Functions of the Gastrointestinal System
- Ingestion
- Secretion
- Mixing and Propultion
- Digestion
- Absorption
- Elimination
Ingestion
Eating
Secretion
Cells in walls of GI tract and accessory organs secrete water, acid, buffers, and enzymes into lumen of tract
Mixing and Propultion
Muscles in organ wall rhythmically contract and relax to mix food and secretions together and move mixture through the system
2 Types of Digestion
- Mechanical
- Chemical
Mechanical Digestion
-Tongue mixes food
-Teeth grind and cut food
-Stomach and small intestine churn/mix food
Chemical Digestion
-Enzymes help break larger nutrients into smaller ones (which can then be absorbed)
-Enzymes are secreted by salivary glands, tongue, stomach, pancreas, small intestine
Absorption
-Taken in through membranes of cells lining stomach and small intestine
-Enters blood or lymphatic systems
-Circulated throughout body
Elimination
-a.k.a. defecation
-Feces: wastes, undigested substances, unabsorbed substances, bacteria, cells sloughed off from GI tract lining
Feces
wastes, undigested substances, unabsorbed substances, bacteria, cells sloughed off from GI tract lining
Mastication
Chewing
Deglutition
Swallowing
Emesis
Vomiting
Gustation
Taste
Teeth
Cut/grind food, mix with saliva, make food more manageable to swallow (mastication/mechanical digestion)
Toungue
Skeletal Muscle covered in mucous membrane
Salivary Glands (Major Ones)
-Parotid
-Submandibular Glands
-Sublingual Glands
Parotid
Inferior and anterior to ear, between skin and masseter
Submandibular Glands
Floor of mouth
Sublingual Glands
Beneath tongue
Saliva
Water, Solutes, Enzymes
Bolus
Soft, flexible mass that is swallowed (i.e. passes into the pharynx)
Pharynx
-a.k.a. throat
-Skeletal muscle lined with mucous membrane
-Muscle contractions move bolus from the mouth into pharynx into esophagus
Esophagus
-Skeletal and smooth muscle
-Collapsible muscular tube sitting posterior to trachea
-Runs from lowest segment of pharynx through diaphragm ( esophageal hiatus) to superior aspect of stomach
-Peristalsis: Wave-like contractions of smooth muscle lining walls of GI tract that move bolus along tract (from esophagus to anus)
-Passage of food from pharynx into esophagus controlled by upper esophageal sphincter
-Passage of food from esophagus into stomach controlled by lower esophageal sphincter (LES)
What is the Function of the Esophagus?
Secrete mucous & transport bolus to stomach
Peristalsis
Wave-like contractions of smooth muscle lining walls of GI tract that move bolus along tract (from esophagus to anus)
Passage of food from the esophagus into the stomach is controlled by the ____________________.
Lower esophageal sphincter (LES)
Passage of food from the pharynx into the esophagus is controlled by the __________________.
Upper esophageal sphincter
Layers of the GI Tract
Wall of the GI tract from lower esophagus to anal canal has same 4 layered arrangment
What are the layers of the GI Tract from deep to superficial?
- Mucosa
- Submucosa
- Muscularis
- Serosa
Mucosa is a mucous membrane consisting of?
-Epithelium
-Lamina Propria
-Muscularis Mucosa
Epithelium
-Epithelial cells
-Exocrine cells (secrete mucous, liquid)
-Enteroendocrine Cells (secrete hormones)
Lamina Propria
-CT (areolar)
-Blood and Lymphatic Vessels (for absorption)
-Mucosa-associated lymphatic tissue (MALT) (for immune function/protection)
Muscularis Mucosa
Smooth muscle layer creates folds in mucosa
Submucosa
-CT layer binds mucosa to muscularis layer
-Contains many blood & lymphatic vessels (for nutrient transport)
-Contains neurons of enteric nervous system for GI control
Muscularis
Skeletal muscle: mouth, pharynx, upper 2/3rds of esophagus, external anal sphincter
Smooth muscle: everything else
Generally in 2 layers:
-Circular fibres
-Longitudinal Fibres
Contractions Help:
-Break down food
-Mix food with secretions
-Move food through GI Tract
Contractions (frequency and strength) controlled by enteric nervous system
Serosa
-Serous membrane
-Outermost layer of organs in abdominal cavity
-a.k.a. visceral peritoneum
What are the 2 layers of Peritoneum?
-Viceral Peritoneum (a.k.a. the Serosa)
-Parietal Peritoneum
Between the 2 layers of the Peritoneum is the __________.
Peritoneal Cavity
Some organs (kidney, ascending and descending colons, duodenum, pancreas) are covered by the peritoneum on their anterior side only they are called ________________.
Retroperitoneal
The Peritoneum contains?
Large folds bind organs to one another and to walls of the abdominal cavity
Stomach
-J-shaped enlargement of GI tract
-Sits immediately below diaphragm
-Runs from esophagus to small intestine
-Can expand to hold several litres
-Food enters stomach through LES
-The stomach mixes food for 2-4 hours
-The soupy mix of food in stomach called chyme
-Little to no absorption happens in stomach (water, ions, some fats, medications, alcohol)
-Once food particles are small enough, they pass through pyloric sphincter into small intestine
The wall of the stomach has the same 4 layered arrangement with some additions which are?
- Specialized Cells
- Additional layer of smooth muscle
Mucosal layer has specialized cells that secrete?
- Mucous (mucous neck cells)
- Intrinsic factor and HCL (parietal cells)
- Pepsinogen and Gastric Lipase (Chief Cells)
- Gastrin (Hormone secreted by G cells)
-Stimulates gastric juice production
-Strengthen LES contraction
-Increases stomach peristalsis
-Relaxes the pyloric sphincter - Secretions from mucous, parietal and chief cells (G cells not included) are collectively called gastric juice
Mucous
Mucous Neck Cells
Intrinsic factor and HCL
Parietal Cells
Pepsinogen and Gastric Lipase
Chief Cells
Gastrin
Hormone Secreted by G Cells-Stimulates gastric juice production
-Strengthen LES contraction
-Increases stomach peristalsis
-Relaxes the pyloric sphincter
Secretions from mucous, parietal and chief cells (G cells not included) are collectively called ____________.
gastric juice
Muscularis has an additional (oblique) layer of smooth muscle to _______________.
Facilitate Mixing
Small Intestine
~ 3m long and 2.5cm diameter
Large surface area for digestion & absorption
3 Regions:
-Duodenum
-Jejunum
-Ileum
Circular folds: ridges in mucosa/submucosa that increase surface area
Mucosal layer has villi - finger like projections increase surface area
Each villus is covered in epithelium
Cells of the epithelium:
-Absorptive Cells (digestion/absorption)
-Goblet Cells
-Paneth Cells
-Enteroendocrine cells (secrete hormones)
Absorptive cells have microvilli (brush border)
Each villus has an arteriole, a venule and a lacteal
What are the 3 regions of the small intestine?
- Duodenum
- Jejunum
- Ileum
Circular folds
Ridges in mucosa/submucosa increase surface area
What are the cells of the epithelium?
-Absorptive Cells (digestion/absorption)
-Goblet Cells
-Paneth Cells
-Enteroendocrine cells (secrete hormones)
Mucosal layer of small intestine has?
Villi - finger like projections increases surface area
Each villus in the small intestine is covered in?
Epithelium
In the small intestine absorptive cells have?
Microvilli (brush border)
in the small intestine each villus has an?
Arteriole, a Venule and a Lacteal
Intestinal and pancreatic juices absorbed nutrients pass into either?
-Blood stream (carbohydrates, proteins, water, electrolytes, water-soluble vitamins) and go to liver
-Lymphatics (lipids) via a lacteal
-Remaining food passes through ileocecal valve/sphincter into large intestine
Pancreas
-Posterior to stomach
-Both endocrine and exocrine functions
-Exocrine Function: Secretes pancreatic juice (water, salts, sodium bicarbonate, enzymes) into duodenal lumen
-Juices are secreted into proximal duodenum via 2 main ducts:
1.Common duct formed by pancreatic duct joining common bile duct from liver gallbladder
2. Accessory duct
What is the Pancreas Exocrine Function?
Secretes pancreatic juice (water, salts, sodium bicarbonate, enzymes) into duodenal lumen
In the Pancreas juices are secreted into the proximal duodenum via 2 main ducts which are?
-Common duct formed by pancreatic duct joining common bile duct from liver gallbladder
-Accessory duct
Liver
Sits inferior to diaphragm in right superior region of abdominal cavity
2 Lobes: larger right & smaller left
Receives blood flow from 2 sources:
-Hepatic Artery - Oxygenated Blood
-Hepatic Portal Vein - Deoxygenated blood containing absorbed nutrients, medications, microbes and toxins
Blood flows past hepatocytes (liver cells)
Hepatocytes:
-Absorb oxygen, nutrients, & toxins
-Release nutrients (needed by other cells)
Blood eventually flows into hepatic vein
Hepatocytes also manufacture & secrete bile
What are the 2 Lobes of the Liver?
larger right & smaller left
Liver receives blood flow from 2 sources which are?
-Hepatic Artery - Oxygenated Blood
-Hepatic Portal Vein - Deoxygenated blood containing absorbed nutrients, medications, microbes and toxins
Hepatocytes
-Absorb oxygen, nutrients, and toxins
-Release nutrients (needed by other cells)
Blood eventually flows into hepatic vein
Hepatocytes also manufacture and secrete bile
Carbohydrate Metabolism (Liver)
-Helps Maintain blood Sugar Levels
-Low blood Sugar - Hepatocytes breakdown glycogen & release glucose into the blood
-High Blood Sugar - Hepatocytes remove glucose from blood & store it (as glycogen and fats)
-Can convert some amino acids, lactic acid, & other sugars into glucose
Lipid Metabolism (Liver)
-Hepatocytes store fat, break it down (to make ATP), & make cholesterol
Protein Metabolism (Liver)
-Makes amino acids available for energy
-Can convert amino acids into carbs or fats
-Synthesizes most plasma proteins
Drug and Hormone Processing (Liver)
-Detoxifies inactivates substances (drugs, alcohol, hormones)
-bilirubin elimination
-vitamin & mineral storage
-vitamin D activation
Gallbladder
-Pear-shaped organ sitting in posterior surfac of liver
-Stores & concentrates bile
Bile
-Yellow/brown/olive liquid
-Made by hepatocytes
-Collects into larger & larger vessels
Bile (function)
emulsification (breakdown) of fats
Half Life (medication)
Time 50%
Onset of action (medication)
30min
Large Intestine
-Food enters from small intestine (Ileum) through ileocecal valve/sphincter
What are the 4 main regions of the large intestine?
-Cecum
-Colon
-Rectum
-Anal Canal
Large Intestine (functions)
Completion of absorption, vitamin K production, formation & elimination of feces
Cecum
-Small pouch attached to ileocecal valve
-Attached to the cecum is appendix
-Contents move from cecum into colon
What are the 4 portions of the Colon?
-Ascending (to the hepatic flexture)
-Transverse (to the splenic flexure)
-Descending (to the left iliac crest)
-Sigmoid (to the rectum at ~S3)
Colon
-As food accumulates in ascending colon, haustra fill up/distend which stimulates smooth muscle contraction & food moves into next haustra
-Regular peristalsis occurs but more slowly
-With each meal, mass peristalsis moves feces from transverse colon into rectum
Rectum
-Travels inferiorly to the anal canal
Anal Canal
-Terminal portion of large intestine
-Elimination control: Internal (involuntary control) & external (voluntary control) anal sphincters
Defecation Reflex
Distension of rectum ultimately gives urge to go & relaxes internal anal sphincter
Divisions of GI Tract
-Upper GI
-Lower GI
Upper GI
Mouth, Pharynx, Esophagus, Stomach, Duodenum
Lower GI
Most of intestines & anus
What are the 3 overlapping phases of digestion?
-Cephalic
-Gastric
-Intestinal
Cephalic Phase
-The thought, small, sight, initial taste of food activates the NS
-Salivary and gastric glands are stimulated to prepare mouth & stomach for digestion
Gastric Phase (once food reaches the stomach)
-Stretch receptors are stimulated by change in stomach shape
-Chemo receptors are stimulated by change in stomach PH
Gastric Phase (changes after food reaches stomach)
-Increase peristalsis & gastric juice production
-Stimulate gastrin release
Gastric Phase
Once food reaches stomach:
-Stretch receptors are stimulated by change in stomach shape
-Chemo receptors are stimulated by change in stomach PH
These changes:
-Increase peristalsis & gastric juice production
-Stimulate gastrin release
-Small amounts of chyme pass through pyloric sphincter into duodenum
-Food leaving stomach decreases volume of the stomach and removes some of the stimulus from stretch receptors
-Food leaving stomach allows stomach to become more acidic
-Decreasing stretch receptor stimulation & normalizing PH removes some of the stimulus for gastrin release
Intestinal Phase
-Chyme in duodenum causes enteroendocrine cells to release hormones:
-Cholecystokinin (CCK)
-Secretin
These Hormones:
-Stimulates gallbladder to eject bile into duodenum (CCK)
-Secretin decrease gastric juice production (CCK/Secretin)
-Slow food coming through pyloric valve (CCK/Secretin)
-Increase pancreatic juice secretion (CCK/Secretin)
Endocrine System
-System of glands & cells that secrete hormones to regulate & integrate body systems
-Control System
-Endocrine Glands: Organs that secrete substances into the blood in response to stimuli
-Glands work slower (seconds-hours-days)
Endocrine Glands
Organs that secrete substances into blood in response to stimuli
Hormones
-Chemical messengers (a.k.a. mediator molecules)
-Released into interstitial fluid which then enter bloodstream and via the circulation, have access to body cells
-They are released in one part of body to regulate activity in another
Hormone Receptors
-To function (deliver message) hormones must bind to receptors on cell membranes of target cells/organs
-When hormone binds to receptor, it changes shape of receptor
-Changing the receptor’s shape activates pathways that modify cellular functions (i.e. message is delivered)
-One hormone can regulate several different body functions
-One body function can be regulated by several different hormones
Upregulation
-Increase in target cell receptors due to lack of circulating hormone
-Increases sensitivity to hormone
Down Regulation
Decrease in target cell receptors due to an excess of circulating hormone
-Decreases sensitivity to hormone
Hormone Levels
-Most hormones are present in body all the time (usually in small amounts)
-Levels fluctuate depending on demand & normal body rhythms
-Normal levels can be altered by environment, stress, inflammation, pathologies
-Normal rhythms often absent in disease states
Secretion Control
-Nervous System
-Chemical changes in blood
-Other Hormones
-In most cases, hormone levels are managed through negative feedback loops
Primary Glands
-Pituitary
-Thyroid
-Parathyroid
-Adrenal
-Pineal
Other Organs that Secrete Hormones
-Hypothalamus
-Thymus
-Ovaries/Testes
-Pancreas
-Kidneys
-Stomach & Small Intestine
-Heart
-Adipose tissue
-Placenta
-Liver
-Skin
Hypothalamus & Pituitary
-These 2 regulate all aspects of growth, development, metabolism, & homeostasis
Hypothalamus
-Major integrating centre between nervous & endocrine systems
-Receives input/information from many different structures
-Controls ANS, regulates synthesis & release of anterior pituitary hormones
-Neurologically, regulates synthesis & release of posterior pituitary hormones
Pituitary
-a.k.a. Hypophysis
-Small gland, sits in sella turcica of sphenoid bone
-Has 2 lobes:
1. Anterior lobe (a.k.a. Adenohypophysis)
2. Posterior Lobe (a.k.a. Neuhypophysis)
Anterior Pituitary
-Release or inhibition of it’s hormones is controlled hormonally by hypothalamus
Hormones:
-Human Growth Hormone (hGH)
-Thyroid Stimulating Hormone (TSH)
-Adrenocorticotropic Hormone (ACTH)
-Luteinizing Hormone (LH)
-Follicle Stimulating Hormone (FSH)
-Prolactin (PRL)
-Melanocyte Stimulating Hormone (MSH)
Human Growth Hormone (hGH)
-Stimulates tissue growth
-Promotes healing & tissue repair
-Increase use of lipids for energy
-Decreases cellular uptake of glucose/elevates blood glucose levels
-hGH is released in bursts every few hours
Factors that promote Release of Human Growth Hormone (hGH)
-Hypoglycemia
-Deep sleep (stages 3 & 4 or non REM)
-Increased SyNS (e.g. vigorous exercise)
-Other hormones (glucagon, cortisol, insulin, estrogens)
Factors that inhibit Release of Human Growth Hormone (hGH)
-Hypoglycemia
-REM sleep
-Obesity
-Low levels of thyroid hormones
-High levels hGH in the blood (negative loop)
Thyroid Stimulating Hormone
-Stimulates release of thyroid hormones by thyroid gland
-Its release is dependent on level of thyroid hormones in blood
Adrenocorticotropic Hormone
-Stimulates release of cortisol from adrenal glands
-Release increases with stress-related stimuli (e.g. injury, hypoglycemia), macrophage activity
Luteinizing Hormone (LH)
-Females: Triggers ovulation
-Males: Stimulates testes to release testosterone
Follicle Stimulating Hormone (FSH)
-Females: Triggers ovarian follicle development
-Males: Triggers sperm production in testes
Prolactin (PRL)
-Initiates and maintains milk production in mammary glands
Posterior Pituitary
-Release or inhibition of it’s hormones is controlled neurological by hypothalamus
Hormones:
-Oxytocin
-Antidiuretic Hormone (ADH) (a.k.a. Vasopressin)
Oxytocin
-During delivery, enhances smooth muscle contraction of the uterus
-Post-partum, stimulates milk ejection
Antidiuretic Hormone (ADH)
-Decreases urine production
-Causes arteriolar vasoconstriction
Factors that promote Antidiuretic Hormone (ADH)
-Dehydration
-Pain/Stress/Anxiety/Trauma
-Nicotine
-Some Medications
Factors that inhibit Antidiuretic Hormone (ADH)
-Increased blood volume
-Alcohol
Thyroid Gland
-Inferior to larynx
-Produces thyroid hormones & calcitonin
-Activity is controlled by hypothalamus-pituitary
Thyroid Hormones
-Increase basal metabolic rate
-Maintain body temp
-Stimulate protein synthesis
-Increase use of glucose & lipids to generate ATP
-Mobilize lipids & enhance cholesterol excretion
-Enhance the actions of norepinephrine & epinephrine (= increase HR, increase Heart contractility, increase BP)
-With hGH & insulin, body growth accelerates
Calcitonin
-Decreases blood calcium levels by inhibiting osteoclast activity
Parathyroid Gland
-Located on posterior aspect of thyroid gland
-Secrete parathyroid hormone (PTH)
-Increase blood calcium, magnesium, & phosphate levels by increasing number & activity of osteoclasts
-Also works on kidneys to decrease their secretion of calcium & magnesium & promote the formation of calctriol (active form of vitD)
Adrenal Glands
-Each has Adrenal Cortex & Adrenal Medulla
Adrenal Cortex Releases
- Aldosterone
- Cortisol
- Androgens
Adrenal Medulla Releases
- Epinephrine (adrenaline)
- Norepinephrine (noradrenaline)
Adrenal Cortex (Aldosterone)
-Regulates sodium & potassium levels
-Helps regulate blood pressure/volume
-Helps in elimination of H+ (acid)
-Stimulates kidneys to reabsorb sodium & water & stimulates arteriolar smooth muscle contraction
-Released in response to dehydration, sodium deficiency, hemorrhage
Adrenal Cortex (Cortisol) a.k.a. stress hormone
-Regulates metabolism & provides resistance to stress
-Makes energy available to help body deal with ‘stress’ (whatever that may be: exercise, fear, bleeding, surgery…)
-Stimulates processes that increase/maintain blood glucose concentrations
-Helps body resist stress by making more energy substrate available & facilitating vasoconstriction
Cortisol a.k.a. stress hormone - Effects on glucose metabolism
-Maintains blood glucose during fasting
-Increases blood glucose during stress (at expense of muscle & adipose tissues) through gluconeogenisis
-Decrease use of glucose by the tissues
Cortisol a.k.a. stress hormone - Effects on protein metabolism
-Increase protein breakdown
Cortisol a.k.a. stress hormone - Effects on lipid metabolism
-Increases lipids in bloodstream
-Increases use of lipids by the tissues
Cortisol a.k.a. stress hormone - Effects on inflammatory response
-Inhibits it
-Also slows tissue repair
Cortisol a.k.a. stress hormone - Effects on immune system
-High doses depress immune responses
Cortisol a.k.a. stress hormone - Effects on cardiovascular system
-Stimulates erythropoietin (EPO) production
Cortisol a.k.a. stress hormone - Effects on reproductive system
-Inhibits reproductive function
Cortisol a.k.a. stress hormone - Effects on skeletal system
-Increases bone resorption (removal of calcium from bone & into blood)
-Inhibits osteoblast function
Cortisol a.k.a. stress hormone - Effects on connective tissue
-Inhibits fibroblast proliferation and collagen formation
-With excessive amounts of cortisol, skin thins and CT support of capillaries is impaired leading to increased bruising
Cortisol a.k.a. stress hormone - Effects on renal system
-Inhibits ADH secretion
-Increases formation of urine (increased GFR)
Cortisol a.k.a. stress hormone - Effects on muscle system
-Excessive levels lead to muscle weakness & pain
*Cortisol a.k.a. stress hormone - Effects on GI system
-Stimulates appitite
-Stimulate acid and pepsin secretion (increases risk of ulcer development)
Adrenal Cortex (Androgens)
-During puberty: stimulate axillary & pubic hair growth
-Males (after puberty): weak
-Females (after puberty): function in libido & are converted to estrogens
Adrenal Medulla
-Produces norepinephrine (noradrenaline), epinephrine (adrenaline)
-Both are released during stress & exercise - Increase SyNS response
Pineal Gland
-Secretes melatonin to regulate sleep cycles
-Increased secretion in darkness, decreases secretion in sunlight
Thymus
Hormones promote maturation of T cells
Ovaries
-Secrete estrogens & progesterone which (along with FSH and LH) regulate menstrual cycle, maintain pregnancy & prepare mammary glands for lactation
-Initiate/maintain secondary female sex characteristics
-With placenta, they secrete relaxin which increases tissue/joint compliance in preparation for delivery
Testes
-Secrete testosterone which regulates sperm production & initiates/maintain secondary male sex characteristics
Pancreas
-Located in duodenum
-Pancreatic islets (islets of Langerhans) are endocrine cells which secrete:
1. Glucagon
2. Insulin
3. Somatostatin
Pancreatic islets (islets of Langerhans) are the endocrine cells which secrete
- Glucagon
- Insulin
- Somatostatin
Glucagon
-Increases blood glucose levels
-Stimulates hepatocytes to release glucose from their stores
-Triggers by hypoglycaemia, exercise
Insulin
-Decreases blood glucose levels
Stimulates:
-Body cells to take up glucose from blood
-Hepatocytes to uptake & store glucose (as glycogen)
-Hepatocytes to slow their release of glucose
-Triggered by hyperglycaemia
-Also triggered by hGH, ACTH, PaNS, some amino acids, & GI tract
Somatostatin
-Inhibits glucagon & insulin release
-May slow GI absorption
Other Endocrine Organs (secondary)
-Kidneys
-Stomach/Intestine
-Heart
-Adipose
-Placenta
-Liver/Skin
Other Endocrine Organs (secondary) *Kidneys
Erythropoietin (EPO) stimulates RBC production, calcitriol (active form of vitD)
Other Endocrine Organs (secondary) *Stomach/Intestine
Gastrin, CCK, Secretin
Other Endocrine Organs (secondary) *Heart
Atrial naturetic peptide (ANP) decreases BP
Other Endocrine Organs (secondary) *Adipose
Leptin suppresses appetite
Other Endocrine Organs (secondary) *Placenta
Human chronic gonadotropin (hCG) helps maintain pregnancy
Other Endocrine Organs (secondary) Liver/Skin
Calcitriol (active form of vitD) - start in skin, continues in liver, ends in kidneys
