Chapter 23: The Digestive System Study guide

Primary functions of the digestive system

• Break down the foods you eat

• release their nutrients

• absorb those nutrients into body

Trace the GI tract including accessory structures

Mouth > pharynx > esophagus > stomach > small intestine (duodenum > jejunum > ileum) > large intestine (cecum > ascending colon > transverse colon > descending colon > sigmoid colon) > rectum > anus

List the major peritoneal folds including their locations

• Greater momentum, located superficial to small intestine & transverse colon

• Falciform ligament, anchors liver to anterior abdominal wall & inferio border of diaphragm

• Lesser omentum, suspends stomach from inferior border of liver & provides a pathway for structures connecting to liver

• Mesentery, vertical band of tissue anterior to lumbar vertebrae & anchoring all the small intestine except the duodeunum

• Mesocolon: attaches 2 portions of large intestine to postrrio abodminal wall

Define ingestion, propulsion, mechanical + chemical digestion, absorption, defection, and where each occur.

• Ingestion: entry of food into alimentary canal & occurs in mouth

• Propulsion: the movement of food & occurs in digestive tract

• Mechanical + chemical digestion: mechanical digestion is a physical process that doesnt cause the process of food & occurs in the mouth, stomach and small intestine; chemical digestion starts in the mouth & digestive secretions break down complex food meolcules into their chemical building, occurs in small intestine

• Absorption: taking digested foods into bloostreamn or lymph, occurs in small intestine

• Defecation: undigested materials are removed from body as feces, occurs in anus

List and define the different types of papillae found on the tongue

• Fungiform papillae: tend to be larger towards the rear part of tongue & smaller on the tip and sides and contain taste buds

• Filiform papillae: long & thin, have touch receptors that help tongue move food around in mouth, and create an abrasive surface that performs mechanically

• Circumvallate papillae: large circular bumps on back of tongue & primary function is taste perception

Name the three types of salivary glands, including location. Why is saliva important?

• Submandibular glands - located on floor of mouth

• Sublingual glands - located below the tongue

• Parotid gland: located between the skin & masseter muscle

Saliva is important because it lubricates food to form a bolus for easier swallowing, contains enzyme salivary amylase which intiates the breakdown of carbohydrates, contans immunoglobulin A which makes saliva antimicobial, and its pH balance (6.35-6.85) and helps neutralize acids.

Describe the three regions of the pharynx. Do all play a role in the digestive system? Include

the epiglottis in your response.

• Nasopharynx - most superior, involved only in breathing & speech

• Oropharynx - begins inferior to the nasopharynx & is continous below with the laryngopharynx

• Laryngopharynx - inferior border of laryngopharynx coonnects to esophagus & anterior portions connects to larynx and involved

Only the oropharynx & laryngopharynx play a role in digestion. They also play a role in breathing and at the bottom of laryngopharynx splits into the esophagus and larynx and the epiglottis sits at that split and folds down and covers the opening of the larynx when you swallow. This forces the food to go from pharynx into the esophagus.

Compare and contrast esophageal sphincters

Upper esophageal sphincter

• Controls movement of food from pharynx to esophagus

• Prevents air from entering esophagus while breathing

• It is a skeletal muscle

• Voluntary control

Lower esophageal sphincter

• Located between the esophagus & stomach

• Relaxes to let food pass into stomach & contracts to prevent stomach acids from backing up into esophagus

Both sphincters are circular muscles that act as valves, they both open & close to control the movement of food, and they help maintain one-way flow through digestive tract

Describe two features that make the stomach different from other major organs along the

GI tract.

• The stomach has an extra layer for churning called the oblique muscle

• The stomach has folds called rugae that flatten when the stomach fills, allowing it to expand

Explain the production of pepsin and what it does

Chief cells in the stomach secrete pepsinogen, which is the inactive protein form of pepsin. Parietal cells are secreting HCI at the same time, which is necessary for the conversion of pepsinogen to pepsin. Pepsin is a protein digesting eznyme, it breaks down large proteins into smaller peptides & is one of the 1st major steps in chemical digestion of proteins in body.

List the regions of the small and large intestines

Small intestine: duodenum, jejunum, and ileum

Large intestine: the cecum, the colon, the rectum, and the anus

Define plicae, villi, microvilli, and lacteal and explain their importance

• Plicae - a circular fold of the mucosa/submucosa of small intestine. Importance: The folds facilitate absorption which makes chyme spiral in small intestine, allowing nutrients time to be full absorbed.

• Villi - hairlike, vasculazrized projections within circular folds. Importance: ncrease the surface area of epithelium because there are 20-40 villi per square milimeter. Also contain a capillary bed & lacteal for nutrient absorption.

• Microvilli - cylindrical apical surface extensions of plasma membrane of mucosas epithelial cells & are supported by microfilaments. Importance: expand the surface area of plasma membrane & enchances absorption because there are estimated 200 million microbial per square milimeter of small intestine and contains enzymes that finish digesting carbohydrates & proteins

• Lacteal: lympathic capillary inside each villus. Important: absorb breakdown products & transport them to the bloodstream via the lymphatic system

List and explain the importance of accessory organs, including their secretions

• Liver - secretes bile while emulsifies fats and make digestion fst & absorption easier

• Pancreas - secretes pancreatic juice and is the major organ for chemical digestion & protects small intestine from acid

• Gallbladder - doesn’t secrete bile, but instead stores & concentrates bile from the liver and releases bile into small intestine when fatty food is present

• Salivary glands: secerets saliva and lubricates food, forming a bolus, to make it easier for swallowing and begings carbohydrate digestion

Explain the importance of the hepatic portal system. Include how it impacts drug usage as

well as its role in cancers

• Importance: The liver stores nutrients, regulates blood nutrient levels, and removes toxins & modifies chemicals absorbed from food, which projects the body from sudden spikes in nutrients & harmful substances

• Drug usage: many oral drugs are absorbed in intestines & go to to liver first and may break down part of the drug or reduce the amount of active drug that goes into bloodstream; called the first-pass effect and means some medications are less effective when taken orally.

• Role in cancers: if tumor forms in the GI tract, cancer cells travel through the portal system to the liver, which causes liver to become a common site for metastasis