Digestive Part I Flashcards
What are the 6 Basic Processes for Digestion?
- Ingestion
- Secretion
- Mixing & Propulsion
- Digestion
- Absorption
- Defecation
Digestion begins where & with what two mechanisms?
In the MOUTH
via Mechanical & Chemical Digestion
Mechanical Digestion is accomplished by & creates what?
Mastication
- Food is reduced to a “BOLUS” (easily swallowed mass)
- Saliva begins to dissolve food
Chemical Digestion is accomplished by?
Enzymes secreted in the mouth
Name the enzymes secreted in the mouth.
Salivary Amylase
Lingual Lipase
Characteristics of Salivary Amylase.
- Initiates breakdown of carbohydrates
- Chloride ion: activated in the mouth in saliva
- Stomach acid deactivates
Characteristics of Lingual Lipase.
- Initiates breakdown of lipids (TAGs)
- Activated in the stomach via stomach acid
From the mouth food passes into what when swallowed?
Pharynx
Characteristics of Pharynx.
- Funnel-shaped tube
- Extends from internal nares to esophagus
- Composed of skeletal muscle
- Lined with mucous membrane
What are the three parts of the Pharynx?
Nasopharynx
Oropharynx
Hypo/Laryngopharynx
What part/s of the Pharynx functions in only Respiration?
Nasopharynx
What part/s of the Pharynx function in digestion & respiration?
Oropharynx
Hypo/Laryngopharynx
What specific parts of the pharynx does food pass through when swallowed?
Oropharynx (1st)
Laryngopharynx (2nd)
Characteristics of the Esophagus.
- Collapsible muscular tube
- Usually 10” long
- Lies posterior to the trachea
Esophagus begins where, passes through what structures, & ends where?
Begins: Inferior end of hypo/laryngopharynx
Passes: Through inferior portion of neck, enters mediastinum, & pierces the diaphragm
Ends: Superior portion of stomach
What is the name of the area the esophagus pierces the diaphragm?
Esophageal Hiatus
What is a hiatal hernia?
Portion of the stomach that herniates through the esophageal hiatus
Name the layers (histology) of the Esophagus. (Superficial to lumen)
- Adventitia
- Muscularis
- Submucosa
- Mucosa (3 layers)
What role does the Adventitia layer of the Esophagus play?
Attaches esophagus to surrounding structures
Describe the Muscularis layer.
Superior 1/3 esophagus is skeletal muscle
Middle 1/3 esophagus is skeletal transitioning to smooth muscle
Inferior 1/3 esophagus is smooth muscle
What is contained in the Submucosa Layer of the Esophagus?
Areolar connective tissue
Blood Vessels
Mucous Glands
What are the 3 layers of the Mucosa layer of the Esophagus?
Muscularis mucosae (smooth muscle) Lamina propria (areolar connective tissue) Nonkeratinized stratified squamous epithelium
What benefit is derived from having Nonkeratinized stratified squamous epithelium lining the lumen of the Esophagus?
Considerable protection against abrasion from food particles
What occurs at each end of the esophagus involving the Muscularis layer?
Muscularis layer thickens forming a sphincters
What is the name and function of the most superior sphincter of the Esophagus?
Upper Esophageal Sphincter (UES):
- Skeletal Muscle
- Regulates movement of food from hypopharynx to esophagus
What is the name & function of the inferior sphincter of the Esophagus?
Lower Esophageal Sphincter (LES):
- Smooth Muscle
- Regulates movement of food from esophagus to stomach
Name the different aspects of the physiology of the Esophagus.
- Secretes Mucous (Protective Function)
- Transports food to the stomach
- Does NOT produce Digestive Enzymes
- Does NOT participate in Absorption
What is Deglutition?
The Act of Swallowing
(Movement of food from the mouth into the stomach)
What is involved in the process of Deglutition?
Facilitated by secretion of saliva & mucous
Involves: Mouth, Pharynx, Esophagus
What are the Stages of Deglutition?
- Voluntary Stage
- Pharyngeal Stage
- Esophageal Stage
What is occurring during the voluntary stage of deglutition?
- Swallowing starts when bolus is forced to back of oral cavity
- Bolus travels backward toward the oropharynx by the movement of the tongue upward & backward against the palate
What is occurring during the Pharyngeal Stage of deglutition?
- Bolus moves into oropharynx then through hypo/laryngopharynx & into esophagus
- Bolus stimulates receptors which send impulses to deglutition center in medulla & lower pons
- Nerve impulses cause soft palate & uvula to move upward to close off nasopharynx
- Impulses cause epiglottis to close off larynx
- Bolus moves through oropharynx & hypo/laryngopharynx
What is occurring during the Esophageal Stage of deglutition?
- Begins once bolus enters esophagus
- Peristalsis pushes bolus onward to stomach
How long does it take for solid or semisolid food to travel from mouth to stomach?
4-8 Seconds
How long does it take liquids to travel from mouth to stomach?
1 Second
What are the layers of the GI Tract from lower esophagus to anal canal?
Serosa or Adventitia
Muscularis
Submucosa
Mucosa
The Serosa Layer is found on all parts of the GI except where?
Esophagus
Proximal Portion of Duodenum (closest to stomach)
What is the Serosa layer composed of?
-Areolar connective tissue & simple squamous epithelium (Mesothelium)
What is another name in which the Serosa Layer?
Visceral Peritoneum
What is the Adventitia layer composed of?
Single layer of connective tissue for esophagus & proximal duodenum
What is significant of the Muscularis Layer?
Skeletal Muscle: Voluntary
Smooth Muscle: Involuntary
Where is the voluntary skeletal muscle found?
Mouth, pharynx, superior aspect of esophagus
External anal sphincter
What is significant of the involuntary smooth muscle layer?
- Contains Myenteric Plexus (Plexus of Auerbach)
- Contraction help mix & propel food forward break it down
- Two layers: Inner circular, outer longitudinal
What is the Myenteric Plexus (Plexus of Auerback)?
Network of neurons between the circular & Longitudinal muscle layers
What does the submucosa layer consist of?
- Areolar connective tissue (binds mucosa to Muscularis)
- Blood & Lymph Vessels that receive absorbed food moleules
- Contains Submucosal Plexus (Plexus of Meissner)
How many layers is the Mucosa Layer of the GI Tract consist of?
3 Layers
Name the layers of the Mucosa Layer of the GI Tract from outer to inner?
- Muscularis Mucosae
- Lamina Propria
- Epithelium
What are the characteristics of the Muscularis Mucosae?
- Thin Layer smooth muscle fibers
- Causes the mucous membrane of small intestine & stomach to have the folded appearance
- Folds increase surface area for digestion & absorption
- Movement ensures all absorptive cells are fully exposed to contents
What are the characteristics of the Lamina Propria?
- Areolar connective tissue containing blood & lymphatic vessels (allow nutrients to reach tissues)
- Supports epithelium & binds to Muscularis mucosae
- CONTAINS majority of MALT
What does MALT stand for?
Mucosa-associated Lymphatic Tissue
What is MALT?
-Lymphatic nodular tissue contains immune cells that protect against disease
Where is MALT especially present?
Tonsils
Small Intestine
Appendix
Large Intestine
What are the characteristics of the Mucosa Layer?
- Nonkeratinized stratified squamous cells
- Simple Columnar cells
- Exocrine Cells
- Enteroendocrine Cells
Where is the Nonkeratinized stratified squamous cells found & what is it’s function?
Mouth Pharynx Esophagus Anal Canal -Protective Function
Where is the Simple Columnar cells found & function?
Stomach
Intestines
-Secretion & Absorption
-Tight junctions between cells prevent leakage
What is the function of the Exocrine Cells?
Secrete mucous & fluid into lumen
What is the function of the Enteroendocrine cells?
Secrete hormones into lumen
Name the Neural innervation of the GI Tract?
Intrinsic Nerves (Enteric nervous system) Extrinsic Nerves (Autonomic Nervous System)
What are the characteristics of the ENS?
- “Brain” of the gut
- 100,000,000 neurons esophagus to anus
- Myenteric (Auerback) Plexus
- Submucosal Plexus (Plexus of Meissner)
Where is the Myenteric (Auerbach) Plexus located?
Between Longitudinal & Circular Smooth Muscle Layers of the Muscularis
Where is the Submucosal Plexus (plexus of Meissner) located?
Submucosa
What do each plexuses consist of?
Neurons, interneurouns, sensory neurons
What supplies motor impulses to longitudinal & circular smooth muscle layers of Muscularis?
Myenteric (Auerback) Plexus
The innervation from the Myenteric Plexus provides what?
-Majority of motility of GI tract
Frequency & strength of contraction of Muscularis
What supplies motor neurons of the secretory cells of the mucosal epithelium?
Submucosal (Meissner) Plexus
The innervation from Submucosal Plexus provides what?
Controlling of secretions of the organs of the GI tract
What do the interneurons allow?
Connection of the myenteric & submucosal plexuses
Where are the sensory neurons found?
Supply mucosal epithelium
What are the functions of the Sensory Neurons?
Chemoreceptors
Baroreceptors
What activates the Chemoreceptors?
Certain chemicals in food located in the lumen of GI organs
What activates the Baroreceptors (Stretch Receptors)?
Food stretches distends the wall of GI organs
What purpose does the ANS serve for the GI Tract?
- Helps regulate ENS
- Vagus Nerves (CN-X) supply parasympathetic fibers
- Parasympathetic nerves for neural connections with ENS
Where is the Vagus (CN-X) Nerve not apart of innervation of the GI?
Last half of the large intestine
What innervates the last half of the large intestine?
Parasympathetic fibers supplied from sacral spinal cord
Stimulation of the parasympathetic nerves cause?
Increase in GI secretion & motility by increasing activity of ENS
The ANS Sympathetic nerves arise from where?
Thoracic & Upper Lumbar regions of spinal cord
connections with ENS
What do the Sympathetic nerves cause?
Decrease GI secretion & motility by inhibiting the ENS neurons
What do emotions such as fear “fight-or-flight”, anger, anxiety cause within the GI?
Sympathetic nerves slow digestion
What is the largest serous membrane in the body?
Peritoneum
What does the peritoneum consist of?
- Layer of Simple Squamous Epithelium (Mesothelium)
- Underlying layer of Areolar Connective Tissue
What is the peritoneum divided into?
- Parietal Peritoneum: Lines wall of abdominopelvic cavity
- Visceral Peritoneum: Covers some organs in the cavity & is also considered their Serosa
What is the space between the two layers that contains lubricating serous fluid?
Peritoneal Cavity
What is Ascites?
Excess fluid accumulates in the peritoneal cavity
What is the most common cause of Ascites?
Liver Failure
What is the space behind the peritoneum called?
Retroperitoneal
What organs lie in this space & are covered anteriorly by the peritoneum?
Kidneys Ascending Colon Descending Colon Duodenum Pancreas
This contains large folds that weave between the viscera & bind organs together & abdominal cavity, it contains blood vessels, lymph vessels, & nerves?
Peritoneum
What are the five major folds of the Peritoneum?
Grater Omentum Faciform Ligament Lesser Omentum Mesentery Mesocolon
What are the characteristics of the Greater Omentum?
Largest Peritoneal fold
- Drapes over transvers colon & small intestine
- Double sheet folds back on itself (4 layers)
- Attaches to portions of stomach & duodenum, anterior small intestines, transverse colon
- Contains adipose tissue
- Lymph nodes (macrophages & Ab producing cells)
What are the characteristics of the Falciform Ligament?
- Peritoneal fold attaches the liver to ventral surface of abdominal wall
- Free border contains Ligamentum teres (round ligament; remnant of umbilical vein)
What is the only digestive organ attached to anterior abdominal wall?
Liver
What are the characteristics of the Lesser Omentum?
- Anterior fold in serosa of the stomach & distal duodenum (suspends the stomach & distal duodenum from the liver)
- Pathway for blood vessels entering Liver
- Contains Portal Vein, Common hepatic artery, common bile duct & some lymph nodes
What is the fan shape fold that binds the jejunum & ileum of small intestine to posterior peritoneal wall?
Mesentery
This fold extends from posterior peritoneal wall, wraps around small intestine & returns to origin?
Mesentery
This fold consist of two separate folds that bind portions of large intestine to posterior abdominal wall, carries blood & lymphatic vessels to intestines, holds small intestines loosely in place?
Mesocolon
What do the two separate folds of the Mesocolon bind to?
First binds the transverse colon
Second binds the sigmoid colon
What is acute inflammation of the peritoneum?
Peritonitis
What are some causes of Peritonitis?
Contamination from infectious microbes (Surgical wound, perforation or rupture of abdominal organs/structures)
- Rubbing together of inflamed peritoneal surfaces
- Peritoneal dialysis
The mouth is also known as?
Oral or Buccal Cavity
What forms the Oral/ Buccal Cavity?
Cheeks
Hard & Soft Palates
Tongue
What do the Cheeks consist of?
- External by skin
- Internal Mucous membrane (Nonkeratinized stratified squamous epithelium)
- Buccinator muscles lie in between external/internal surfaces
What are the characteristics of the lips?
- Contain Orbicularis Oris Muscle
- External Skin, Internal Mucous Membrane
- Muscles keep food in the mouth
- Assist in speech
What is the Oral space completely bound by cheeks, lips, gums, & buccal side of teeth?
Oral Vestibule
What is the space that extends from lingual side of teeth back to the fauces?
Oral Cavity Proper
What forms the roof of the mouth & separates the oral cavity from nasal cavity & allows chewing & breathing at the same time?
Palate
What are the two divisions of the Palate?
Hard Palate
Soft Palate
Which palate is the anterior portion of the roof of the mouth, formed by palatine & maxillae bones, covered by mucous membrane?
Hard Palate
Which palate is the posterior portion of the rood of the mouth & is arched shaped muscular partition between oropharynx & nasopharynx , covered with mucous membrane?
Soft Palate
This structure hands from free border of soft palate, conical muscular process, drawn upward during swallowing?
Uvula
The base of the uvula, what are the two muscular fold that run down the lateral sides of the soft palate?
Palatoglossal Arch
Palatopharyngeal Arch
What is the anterior fold that extends to the side of the base of the tongue?
Platoglossal Arch
What is the posterior fold that extends to the side of the pharynx?
Palatopharyngeal Arch
What are the small masses of lymphatic tissue that produce Ab to fight infection?
Tonsils
What are the names of the different tonsils?
Palatine Tonsils
Lingual Tonsil
Pharyngeal tonsils
What is the location of the Palatine Tonsils?
Between the arches
-Most commonly infected & removed
What is the location of the Lingual Tonsil?
Base of the tongue
What is the location of the Pharyngeal Tonsils?
Superior Portion of nasopharynx
What is the other name of the Pharyngeal Tonsils?
Adenoids
Which Tonsils are removed due to closing off of sinus drainage & cause difficulty breathing through the nose?
Pharyngeal Tonsils (Adenoids)
Two types of Salivary Glands; What are the names of the Minor Glands in the lips, cheeks, palate, & tongue?
Labial
Buccal
Palatal
Lingual
Two types of Salivary Glands; What are the names of the Major Glands (Secrete most of the saliva)?
Parotids
Submanibular
Sublingual
What is the location of the Parotid Glands & how does it secrete saliva into the oral cavity?
Inferior & anterior to the ears between skin & masseter muscle
-Secretes via Parotid Duct (Stenson’s Duct)
This duct pierces the buccinators muscle to open into oral vestibule opposite the second maxillary molar (upper)?
Parotid Duct (Stenson’s Duct)
Where are the Submandibular Glands located & how do they secrete into the oral cavity?
- Floor of the mouth, medial & partly inferior to the body of the mandible bone
- Secretes: Submandibullar ducts (Wharton’s Ducts) open either side of lingual frenulum
Where are the sublingual glands located and secrete via what ducts?
Beneath the tongue & superior to submandibular glands
-Lesser sublingual ducts, open into floor of the mouth in oral cavity proper
What does Saliva consist of?
Chemically 99.5% water & 0.5% Solutes
What are some of the solutes within Saliva?
Sodium Potassium Chloride Bicarbonate Phosphate Dissolved gases, various organic substances, Immunoglobulin A, Lysozymes, Salivary amylase
Which glands secrete serous liquid containing salivary amylase?
Parotid Glands
Which glands secrete serous fluid & salivary amylase & contain mucous cells, a thicker version of what the Parotid glands secrete?
Submandibular Glands
These glands secrete mostly mucous cells, it is thicker & only has a small amount of salivary amylase?
Sublingual Glands
What role does water play in Saliva?
Allows for taste by gustatory receptors
Allows for digestive reactions to begin
What do the Chloride ions do within Saliva?
Activate Salivary Amylase (breakdown of starches)
What role does Bicarb & Phosphate ions play in digestion?
Buffer acidic foods
What is the pH of Saliva?
6.35-6.85 (Slightly Acidic)
What wastes are secreted through saliva?
Urea & Uric Acid
What controls Salivation?
Autonomic Nervous System
How much saliva is secreted daily on average?
1-1.5 liters
Which portion of the Nervous System promotes continuous secretion of a moderate amount of saliva, which lubricates mucous membranes & esophagus & helps keep the movements of the tongue & lips moist during speech?
Parasympathetic
Which portion of the Nervous System dominates Salivation during Stress?
Sympathetic
What is Xerostomia?
Dry Mouth & Throat
Impulses for taste are conveyed to two salivary nuclei in the brain stem called?
Superior Salivatory Nuclei
Inferior Salivatory Nuclei
Which fibers return parasympathetic impulse to stimulate salivation?
Facial (CN-VII) Cranial Nerve
Glossopharyngeal (CN-IX) Cranial Nerve
This accessory digestive organ is composed of skeletal muscle covered with a mucous membrane & its associated muscle form the floor of the oral cavity?
Tongue
What does the tongue attach to?
Inferiorly: Hyoid Bone
Styloid process of temporal bone
Mandible
What is the fold of mucous membrane in the midline of the ventral aspect of the tongue & attaches to the floor of the mouth, aids in limiting movement of tongue posteriorly?
Lingual Frenulum
What is the clinical finding if this is abnormally short, rigid, or anteriorly placed; a person is said to be “tongue-tied” because of lack of movement of the tongue?
Ankyloglossia
These glands are found in the lamina propria of the tongue & secrete watery serous fluid that contains lingual lipase?
Lingual Glands (Von Ebners Glands)
What are characteristics of Lingual Lipase?
Acts on 30% of dietary triglycerides but is not activated until in the stomach
What covers the Dorsal & lateral surfaces of the tongue?
Papillae
These are nipple shaped projection of lamina propria covered with stratified squamous epithelium, many contain receptors for gustation & some for touch?
Papillae
What are the different types of Papillae?
Vallate (Circumvallate)
Fungiform
These papillae are approx. 12 form an inverted “V” shaped row at the back of the tongue & each one of the 12 contain 100-300 taste buds?
Vallate (Circumvallate) Papillae
These papillae are mushroom shaped elevation scattered over the entire tongue surface and each contain about 5 taste buds?
Fungiform Papillae