Lab 4 Digestive System_

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Feb 20, 2024

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Lab 4 Diges+ve System Learning Objectives: 1. Identify the structures and organs of the digestive system using the laboratory models and images 2. Describe the functions of each of the digestive system organs. 3. Compare and contrast the histological features of the tissues in the stomach and small intestine. 4. Compare the lengths of each section of the GI tract. ___________________________________________________________________________________________ Introduc+on: Organs of Digestion You must be able to identify all of the terms in bold on models for the lab exam. Oral Cavity - The function is to ingest food. The mouth begins the process of digestion by secreting saliva and mechanically grinding food. - the mouth, or oral cavity extends from the lips anteriorly to its junction with the oropharynx posteriorly. Important contents of the oral cavity are: 1. teeth 2. tongue 3. hard and soft palate Salivary glands 1. parotid gland and duct 2. submandibular gland 3. sublingual gland OpenStax A&P, pg 1100 Oropharynx & Laryngopharynx - oropharynx connects the oral cavity to the pharynx - laryngopharynx continues openings of larynx (at epiglottis) and esophagus - reviewed in the respiratory system Esophagus - The function is to conduct swallowed food from the pharynx above to the stomach below. 1. Esophageal (cardiac) sphincter 1

Stomach - The func*ons include the storage, some diges*on, and release of food into the duodenum. - The cardia is the region nearest to the entrance of the esophagus. - The fundus is the pocket that is superior to the cardia. - The main midpor*on of the stomach is the body . - The antrum is the lower, muscular por*on of the stomach. The antrum is also known as the pyloric region of the stomach. - The greater curvature is the convex lateral side of the stomach. - The lesser curvature is the concave medial side of the stomach. - The pyloris is the pocket nearest the end of the stomach, the pyloric sphincter is a valve that connects the stomach to the small intes*ne. - Inside the stomach are wrinkly folds of *ssue known as rugae . The rugae allow the stomach to expand when food enters the organ OpenStax A&P, pg 1108 Small Intes+ne - Nearly all absorp*on of nutrients occurs in the small intes*ne. To increase absorp*ve area the small intes*ne displays many lumenal modifica*ons, including finger-like projec*ons known as villi . - The proximal por*on of the small intes*ne is the duodenum . - The middle segment of the organ is the jejunum. - The distal por*on of the small intes*ne is the ileum . 2

OpenStax A&P, pg 1114 Large Intestine - LiCle or no diges*on takes place in the large intes*ne (unless due to ac*vity of the gut microbiome); its func*on is largely water and electrolyte absorp*on. During the process of compac*on, mucus secre*on by goblet cells eases movement of fecal material as it forms. - The proximal por*on of the large intes*ne in the cecum . - The vermiform appendix aCaches to the cecum. - The colon is divided into several regions including the ascending colon , transverse colon , descending colon and sigmoid colon . - The rectum is the distal por*on of the large intes*ne. - The anus is the opening to the exterior. 3

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Pancreas - The head of the pancreas sits in curvature of the duodenum. - The pancrea+c duct joins the bile duct before emptying into small intes*ne - Diges*ve products released by the liver and pancreas enter the small intes*ne at the major ampulla. Liver - The liver is composed of four lobes: the leA lobe , the right lobe , the caudate lobe , and the quadrate lobe . - The falciform ligament is a mesentery that helps to separate the leI and right lobes and aCaches the liver to the diaphragm. - Secreted bile travels through bile canaliculi toward the hepa+c duct . Gall Bladder - The gall bladder sits deep to the leI lobe of the liver. - The cys+c duct joins the common hepa*c duct to form the common bile duct . 4

Ac+vity 1 Iden+fy and label the structures of the diges+ve system in diagram and the models in the classroom. Word bank 5 liver esophagus ascending colon duodenum rectum pancreas appendix transverse colon jejunum stomach gallbladder cecum descending colon ileum anus

Activity 2.Label the Accessory Organs of the GI tract and the models in the classroom. Word bank 6 small intestine liver cystic duct right hepatic duct right hepatic duct pancreatic duct pancreas gallbladder common hepatic duct

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Activity 3: Movement of food through the digestive tract. Procedure: Read the text below which describes the journey of food. It has numbered fill in the blanks.Match the numbers to the parts of the digestive tract referred in the text in the to the 24 structures in the table below. Table1 Digestive System When a person smells food, the process of digestion begins. The stomach begins to fill with _(1)_ acid, and the mouth produces _(2)_ in preparation for the upcoming meal. In the mouth, digestion begins with the three salivary glands _(3)_, _(4)_, and _(5)_ produce saliva.The food is chewed and swallowed is now called a bolus, through the _(6)_ and moves down the esophagus by _(7)_. At the diaphragm, the esophagus joins the stomach through a connection called the _(8)_. Once inside the stomach, the bolus of food is able to expand the stomach because of the wrinkly walls called _(9)_. The stomach liquefies the food into a solution known as chyme. This liquid then exits the stomach through the _(10)_ sphincter, which only allows a small amount of the fluid into the start of the small intestine, the _(11)_. Once the acidic chyme is sensed to be in the small intestine, hormones released will regulate the secretion of bile from the _(12)_ and pancreatic juices from the _(13)_. These new enzymes now enter the duodenum and neutralize the chyme. The middle section of the small intestine known as the _(14)_ is where absorption of nutrients occurs with the increased surface area produced by _(15)_, the microscopic finger-like projections from the internal surface of the intestinal tract. 7 Structure # Structure # Structure Villi Ileum Rectum Ascending Colon Ileocecal Junction Rugae Cecum Jejunum Saliva Descending Colon Oropharynx Sigmoid Colon Duodenum Pancreas Sublingual Gland Esophageal Sphincter Parotid Gland Submandibular Gland Gall Bladder Peristalsis Transverse Colon Hydrochloric Acid Pyloric Sphincter Anus

The final segment of the small intestine is known as the _(16)_, where the chemical breakdown of food by enzymes is completed. Next, material moves through the _(17)_ and into the first region of the large intestine at the _(18)_, junction. The main job of the large intestine is to compact the material and create fecal material through compaction. The large intestine has four segments, _(19)_, _(20)_, _(21)_ and _(22)_. After the fecal material travels to the end of the large intestine, it is stored in the sigmoid colon before being released through the _(23)_ and the _(24)_. _____________________________________________________________________________ Activity 4 .Histology of small Intestine Examine a slide of stomach and small intestine. Identify the following features, sketch and label what you see in the space below: I. Stomach 1. Mucosa (simple columnar epithelium, gastric pits, gastric glands) 2. Submucosa (areolar connective tissue) 3. Muscularis externa (circular layer, longitudinal layer) 4. Serosa (fibrous connective tissue) II. Small intestine 1. Plicae circularis (circular folds) 1. Intestinal villi 2. Mucosa (simple columnar epithelium with microvilli) 3. Submucosa (areolar connective tissue) 4. Muscularis externa (circular layer, longitudinal layer) 5. Serosa (fibrous connective tissue) 8

A ctivity 5 : Modeling the length of the digestive tract. Procedure: 1. Digestion begins in the mouth , so measure and cut a piece of white yarn from the front to the back of the mouth. (You can do this by stretching the yarn from the front of your lips to the back of your jaw along your cheek). 2. Record this length of this “mouth” yarn in centimeters (cm)_________________ 3. The esophagus is a tube that connects the mouth and stomach. Measure & cut a piece of yellow yarn the length of the esophagus. (Measure from the back of your jaw to just below your rib cage). 4. Record the length of this “esophagus” yarn in centimeters (cm) in the data table on the next page . Tie or tape the esophagus yarn to the mouth yarn. _________________ 5. In the stomach , gastric juices break down solid food into a liquid. Find the length of the stomach by spreading the fingers of your hand and measuring the span from the thumb to the little finger. Measure and cut a piece of pink yarn to match this length. 6.Record the length of this “stomach” yarn in centimeters (cm) in the data table on the next page. Tie the stomach yarn to the esophagus yarn. ___ 9

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7. The small intestine is the longest part of the digestive system. It is folded up inside of you so it fits. Food is further digested and absorbed here. Measure your height in inches and multiply it by four . Use the red yarn to represent the length of the small intestine. 8. Record the length of this “small intestine” yarn in centimeters (cm) in the data table on the next page. Tie the small intestine yarn to the stomach yarn. 9. Last is the large intestine . It is much wider than the small intestine but much shorter. It is about as tall as you are. Undigested material from the small intestine moves to the large intestine before it leaves your body. Use purple yarn to represent the length of your large intestine. Finally, add up each length to get the total length of your digestive tract in centimeters (cm). Table 2 Length of the digestive system Questions : 1. How does the length of your digestive system compare to your height (if you know your height in feet and inches, convert your height to inches knowing that there are 12 inches in a foot, then multiply it by 0.0254 meters/inch to get your height in meters)? How do you think your digestive system is able to fit inside your abdomen? 10 Digestive Organ Example Length Your length Mouth 10 Oesophagus 38 Stomach 18 Small intestine 650 Large intestine 163 Total length 879

Q2. Why do you think your diges+ve system is so long? How do you think this helps diges+on? What is the longest sec+on of your diges+ve system? What important processes do you think happen to the food in this sec+on? Q3. What percent of your entire digestive system is the small intestine? 11

Lab 4 Digestive System_

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