Digestive System Flashcards

Flashcards covering the histology and anatomy of organs along the GI-Tract.

What is the major function of the anatomy of the digestive system?

To mechanically digest and break apart food; to chemically digest molecules via special secretory cells with enzymes; to maximize overall physiology of absorbing nutrients due to a large surface area.

What is the function of mesenteries in the digestive system?

Route blood vessels, lymphatics, and nerves; hold and support organs in place; store fat for cushioning.

What is the difference between Intraperitoneal and Retroperitoneal organs?

Intraperitoneal organs are suspended from the body wall by dorsal or ventral mesenteries. Retroperitoneal organs have lost their mesenteries during development.

What is 'The Cephalic Phase' referring to in digestion?

Food processing that occurs around the Oral Cavity.

What are the functions of the Thick Stratified Squamous Epithelia lining the walls of the mouth?

Protection against FRICTION and CHEMICALS. Reinforced with Keratin.

What is the function of the Hard Palate?

Provides a rigid surface for the Tongue to push against when Chewing. Ridges help create friction.

What are the TWO types of Skeletal Muscle that make up the Tongue?

Intrinsic and Extrinsic Muscles

What is the general 4-Layer Structure shared by organs of the GI-Tract?

Mucosa, Submucosa, Muscularis Externa, Serosa

What are functions of the Mucosa layer?

SECRETION: Mucus (Lubrication), Enzymes (Digestion), Hormones; ABSORBTION of Nutrients, and transfer to Bloodstream; PROTECTION against Pathogens

What is the function of the Lamina Propria?

This region has both Connective Tissue and Stem Cells to regenerate tissues.

What is the function of the Muscularis Mucosae?

An additional thin muscle layer which is often present to propel Mucus, to help lubrication and protection.

What does the Submucosa contain?

Large amount of Connective Tissue, which helps some organs distend and regain their shape (Stomach); Blood Vessels, Lymph Vessels, and Nerve Fibers (Enteric Nerves)

What is the function of the Muscularis Externa?

Peristalsis (Propulsion of Bolus) = Propulsion of Bolus; Segmentation = Mechanical Digest

What is the function of the Serosa?

OUTERMOST layer i.e., the Visceral Peritoneum that lines system along Body Cavity; Connective Tissue that is covered by single layer of Squamous Epithelia. Can be modified, depending on the organ’s needs…

If the Longitudinal Layer of the GI-Tract runs parallel to the Lumen, what will happen during CONTRACTION?

CONTRACTION will SHORTEN Tube!

If the Circular Layer of the GI-Tract lines circumference the Lumen, what will happen during CONTRACTION?

CONTRACTION will CONSTRICT Cross-Section!

When swallowing, which muscles are VOLUNTARY, and which are INVOLUNTARY?

Tongue/Mouth = VOLUNTARY Skeletal Muscle to initiate the process; Pharynx/Esophagus = INVOLUNTARY Smooth Muscle to move Bolus into the Stomach

What are major functions of the Stomach?

Primarily STORAGE LOCATION for food to be Digested; Protein Digestion is primary chemical digestion role, but it does also produce some Lipases that start fat breakdown; Performs LARGE Amount of the Mechanical Digestion, which turns the food into Chyme

How is the Mucosa of the stomach modified for digestive roles?

With Gastric Glands (their entry are Gastric Pits)

The Muscularis layer has a third innermost layer of smooth muscle. What is it and what is its function?

Oblique Layer: adds “Pummel” to motion that the Smooth Muscle can do, allowing stomach to perform LARGE Mechanical Digestion, in addition to moving it along…

What is contained within the Myenteric Plexus?

Neuronal Ganglia from neurons of the Enteric Nervous System, which regulate Digestion and sending feedback signals

Which cells located in the Myenteric Plexus act as Pacemakers?

Interstitial Cells of Cajal (ICC)

What are the components of Gastric Juice?

Hydrochloric Acid: breakup the ECM holding cells together, and low-PH breaks up larger components, and denatures proteins; Pepsin: once the larger food/cellular components are exposed, the Pepsin enzymes then Digests Proteins into Amino Acids

What is secreted by Parietal Cells?

H+ and Cl- separately into the stomach, and Intrinsic Factor

What is secreted by Chief Cells?

Pepsinogen, which becomes Pepsin when mixed with HCl (low-pH); also secrete Lipases

What is secreted by Mucous Cells?

Mucus to protect lining from Gastric Juice

What are the three structural divisions of the Small Intestine?

Duodenum (first part / entry), Jejunum (highest absorption), Ileum (vitamins, salts / exit)

Where does MOST Digestion occur in the Small Intestine?

Duodenum, where Hormones Regulate Secretions!

What enzymes does the Pancreas send to the Duodenum?

Lipases, Proteases and Nucleases to breakdown fats, proteins, and nucleic acids, respectively

What does the Liver make that is sent to the Duodenum?

Bile Salts, which are first stored in the Gallbladder (breakdown fats)

What maximizes surface area for Absorption in the Jejunum and Ileum?

Brush Border Layer

What projects into the Lumen to increase surface area in the Small Intestine?

Villi

What is secreted by Goblet Cells?

Mucus

What is the function of Enterocytes?

Absorb materials; have microscopic extensions called Microvilli

What tissue extends into the Villi?

Lamina Propria (i.e. Mucosa)

Where do Crypts generally extend down to?

Muscularis Mucosa, at the boundary with the Submucosa

Which vessels transport hydrophilic Amino Acids and Sugars?

Blood Vessels via Capillaries!

Which vessels transport hydrophobic Fats and Glycerides?

Lymph Vessels via Lacteals!

What is secreted by Intestinal Glands a.k.a. Mucosal Glands?

Mucus from Mucosa

Where is Mucus Associated Lymphoid Tissue (MALT) located, and what is its function?

Muscularis mucosae, Immunity Role

What is the function of Peyer’s Patches?

Secrete antimicrobial agents to stop infection; located in the Submucosa of Ileum, near the entry to Large Intestine

To what structure does propulsion of the Chyme conduct in the Small Intestine?

The Ileocecal Valve

What is the initial pocket of the Large Intestine?

Cecum

What is the function of the Cecum?

Pocket below Ileocecal Valve where Chyme can be mixed further with Mucus, and be stored for a time… Aids in Plant Fermentation, through Symbiotic Bacteria, to allow more Absorption, helps the beginning of KEY PROCESSES (Fermentation/Absorption)

What are the TWO Mechanisms via which the Ileocecal Valve RELAXES?

Gastroileal Reflex (Short Reflex) triggered by sensors in Stomach lead to Propulsion in Ileum and RELAXATION of Ileocecal Valve; Gastrin Hormone is mixed into Chyme in the Stomach, which stimulates receptors in the Ileocecal Valve to promote RELAXATION

What role does the Appendix play?

Immunity Role- MALT: Lymphoid Tissue; Helps keep Bacterial Population in-check; Storehouse for “good” Bacteria

What leads to the infection of the Appendix?

Fecal Blockage, due to twisted/narrow structure - Can lead to Appendicitis - Inflammation blocks of drainage…

What processes occur in the Colon?

Fermentation, Absorption of Plant Materials, Absorption of Vitamins, Absorption of Water

What does the Absorption of Water in the Colon cause?

CONCENTRATES the Chyme into Feces

The Longitudinal Layer of muscle in the Colon is reduced to make what?

Tenia Coli

What are the TWO Sphincters in the Anal Canal?

INVOLUNTARY Internal Anal Sphincter; VOLUNTARY External Anal Sphincter

What does the Parasympathetic REFLEX lead to in the Rectum and Anal Canal?

Sigmoid Colon and Rectum CONTRACT; Internal Anal Sphincter RELAXES; Messages relayed to CNS / Brain; Consciously “choose” to complete process; …via External Anal Sphincter