DIGESTIVE SYSTEM Chapter 3 The digestive system consist of the Alimentary Canal….a tube that stretches from the mouth to the anus … and three accessory.

DIGESTIVE SYSTEMChapter 3

• The digestive system consist of the Alimentary Canal….a tube that stretches from the mouth to the anus … and three accessory organs– Liver– Gall bladder– Pancreas

The following image shoes entire system

Alimentary Canal Structure

• The Alimentary canal is organized into 4 functional layers:

• Mucosa:

• Submucosa

• Muscularis

• Serosa

Mucosa:

• This is the site of mucous production

• The mucous aids in transportation, protection and absorption of nutrients

Submucosa

• It lies directly under the mucosa and contains VANL (vein, artery, nerve and lymphatic supply)

• It might also contain specialty glands

Muscularis

• The muscularis is composed of two layers of smooth muscle

• Circular layer

• Longitudinal layer

• These two layers works together rhythmically to create peristalsis to move food along.

Serosa

• The serosa is the most external layer

• It secretes a viscous fluid that helps to reduce friction so that our parts can slip/slide past each other

From the Beginning

• Let’s start from the beginning (oral cavity) and work our way to the finish (anus)

The Oral Cavity

Structures for Study

• Labia

• Tongue

• Teeth

• Salivary glands

• Palate

A lot of structures are found in the mouth…these are the ones we are going to examine

Labia (lips)

Function(s)

• The lips are a sensory organ that detect temperature….reduce the risk of burning

• In terms of digestion, labia also help to keep food in the mouth

Tongue

• Gustatory organ: taste

• Needed for food placement• Needed for proper swallowing• Library.thinkquest.org

Taste

sweet

salty

bitter

sour

Taste cont’

• And for some reason power point would not let me add to the last slide

• Our fifth type of taste is umame (savory) and that occurs over the entire tongue

• Taste is regulated by the taste buds

Taste bud

Taste Buds

• They are embedded within the bumps on the tongues surface.

• They detect chemical concentrations

• The tip of the tongue detects sweet/salty

• Laterally it detects sour

• The rear of the tongue is bitter

• The entire tongue is umame (savory)

Library.thinkquest.org

Tongue Used for Swallowing

Teeth (Dentition)

• Our teeth allows us to be omnivores

• We have teeth for cutting, tearing and grinding

• This ability to be an omnivore is what has made us successful as a species

• Teeth are used for Mastication (chewing)

Tooth Development

• Primary Teeth (deciduous )

• This is our first set….they erupt from 4-6 months and begin to fall out at 6-7 yrs

• We have 20 primary teet• 4 central incisors• 4 lateral incisors• 4 cuspids• 4 primary molars• 4 secondary molars

Secondary Teeth (permanent)

• These are our adult teeth

• All of them should be in by 21

• 32 of these

• 4 central incisors 4 lateral incisors

• 4 cuspids 8 bicuspids (premolars)

• 4 primary molars 4 secondary molars

• 4 tertiary molars

Salivary Glands

• Three groups– Parotid: Cheek area on top of Masseter

muscle– Submandibular: found at the floor of the

mouth– Sublingual: found at the floor of the mouth

Function(s) of Salivary Glands

• Secrete slaiva

• Saliva is mixed with food to create a bolus

• Within saliva we find two prominent enzymes:– Salivary amylase: dissolves carbohydrates– Lingual Lipase: dissolves triglyverides

Enzymes

• In our bodies, enzymes are protein based chemicals that speed up chemical reaction rate and decrease activation energy.

• Because they are protein based, the can be denatured (change shape) and that disrupts function

Denaturing

• Enzymes can be denatured with changes in – pH: to much acid or base can change their

shape– Temperature: Increases in temperature can

destroy enzymes…e.g., high fever

Role of Enzymes

• In the digestive system, enzymes are utilized to reduce macronutrients into a more absorbable micronutrient

• Okay…..back to the oral cavity

Palate

• This is the roof of the mouth

• Divided into the hard and soft palate

• Functions to separate the oral and nasal cavities

• Cleft Palate is developmental dysfunction of the palate

• Please google some images of cleft palate

Pharynx

Divisions

• Nasopharynx: back of the nasal cavity

• Oropharynx: back of the throat

• Laryngopharynx: top of throat

• Pharynx functions as common passageway for respiratory and digestive systems

Esophagus

• Tube extending from laryngopharynx to the stomach

• First instance of sphincters in digestive systems

The Omentum

• The entire gut is covered by a fatty protective sheet called the Greater Omentum

Sphincters

• Sphincters are ring like structures that close tubes to controls

flow

Stomach

Stomach Cont’

• The stomach is a j-shaped organ designed to hold 1 liter of food and fluid

• It is divided into 4 regions (see image):– Cardia– Fundus– Body– pylorus

Sphincters of Stomach

• Cardiac or Lower Esophageal Sphincter: prevents back flow of food from stomach to the esophagus

• Pyloric Sphincter: controls gastric (stomach) emptying

Gastric Pits

• The stomach is lined with gastric pits

• These pits increase surface area and contain specialty cells

Gastric Pit Cells

• Mucous cells: secrete huge amounts of protective mucous

• Parietal cells: secrete hydrochloric acid (HCl) and intrinsic factor…what are the functions of these chemicals?

• Chief cells: secrete pepsinogen and gastric lipase (function?)

• g- cells: secrete Gastrin ( function?)

Function(s) of the Stomach

• The stomach takes the bolus from the mouth and mixes it with gastric juice to create chyme

• It allows absorbs some nutrients…water

• Food typically stays in the stomach for 1-3 hours

• Describe gastric bypass surgery

Small Intestines

Divisions of the Small Intestines

• Duodenum: first 15 or so inches of the S.I. it is the where the accessory organs enter the digestive system. It is the workhorse of the gut

• Jejunum: middle third. Site of nutrient absorption

• Ileum: the end of the S.I. get huge production of mucous in this division…and some absorption

Mesentary

Mesentary

• The mesentary anchors the small intestines to the body. It holds a lot of VANL suppy for the digestive system

Accessory Organs

• Liver

• Gall bladder

• Pancreas

Liver

• Divided into 4 lobes and is anchored back to the diaphragm via the Falciform Ligament

Functions

• Produces bile

• Metabolizes micronutrients

• Detoxifies the blood

• Stores nutrients

• Destroys old red blood cells

Gallbadder

• Small sac that sits underneath the liver

• It stores and concentrates bile

• It secretes bile via the common bile duct into the duodenum

Bile

• Is a cholesterol based product that emulsifies dietary fat

• It breaks fat down into micelles so that the fat can be suspended in water and has more surface area for enzymes to act upon it

Pancreas

• Functions as an exocrine and endocrine gland

Exocrine Gland

• Secrete their product through a duct to the outside of the body or into a hollow organ

• The pancreas secretes digestive enzymes and sodium bicarbonate into the duodenum via the pancreatic and common bile duct

Endocrine Gland

• Secretions are released into the bloodstream and travel to a target cell, tissue or organ

• The pancreas secretes the hormones insulin, glucagon and a few others will we not explore

Accessory Organ Secretions

Large Intestines

Large Intestines

• Approximately 3 feet in length

• Function to transport waste and remove water from waste

Large Intestines Divisions

• Cecum

• Appendix

• Ascending colon

• Transverse colon

• Descending colon

• Sigmoid colon

• Rectum

• Anus

Sphincters of the Large Intestines

• Ileocecal Valve: between the ileum and cecum

• Internal Anal Sphincter: under involuntary control.

• External Anal Sphincter: develops voluntary control at approximately 18 months of age

Summary of Digestive Fluid Production and Secretion

Digestive Pathologies for Study

• Peptic ulcer

• IBS

• GERD

• Crohn’s Disease

• Celiac Disease

• Diverticulosis

• Please learn each of these disorders