The Digestive System: Marco Sesar Per. 5

Functions

Major Organs

Digestive Enzymes

Location of Digestion and Absorption of Each Macromolecule

Layers of GI Tract

Disorders

Digestion of food for metabolism

Absorption of food for metabolism

Mastication

Chewing Movement

Segmentation

Mixing/churning movement

Peristalsis

Wave/rippling movement

Small Intestine

Absorbs-water, vitamins, minerals, carbohydrates/proteins, and fats

Large Intestine

Absorbs-water, vitamin K, and B complex

Primary Processes

Motility/Propulsion

Secretion

Digestion

Absorption

Ingestion

Elimination/Defication

Eating

physical (teeth) and chemical (enzymes) breakdown of food into nutrients

Mixing and movement of food (muscles)

release of mucus, acid, bile, and enzymes to aid digestion

Taking in of nutrients

removal of waste and undigested food from the body

Mucosa

Submucosa

Muscularis

Serosa

Mucous membrane produces mucus for reduction of friction and protections

Epithelium

Varies by location

Nonkeratinized stratified squamous in mouth, esophagus, and anus

Protection against friction

Simple columnar in intestine for absorption and secretion

Lamina Propria

Areolar CT. contains blood and lymphatic vessels, and lymph node for nourishment and immunity

Muscularis mucosae

Two thin layers of smooth muscles

Autonomic nerve supply

Areolar CT containing major BV

Many elastic fibers to retain shape

Submucosal plexus

Glands and lymphatic tissue

Muscle Layer

2 layers of smooth muscles to allow peristalis and segmentation

Inner circular layer

Squeeze, decrease size of lumen; in some areas act as sphincter or valves

Outer longitudinal layer

shortens intestine

Mouth, pharynx, superior esophagus, and anal sphincter-voluntary muscle

Also external and sphincter is skeletal muscle

Myenteric plexus-nerves

Outer covering of the Gi Tract

Serous membrane

Composed of thin layer of areolar CT and simple squamous epithelium

Produces serous fluid for lubrication

Covers the outside of abdominal organs

Attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries

Pepsin-protein-peptide

Carbohydrates(mouth and small intestine)

Protease-peptide-amino acids

Polysaccharides-dissacharides and monosacharides

Amylase-poly-di

Dissacharides-monosaccharides

Maltase-glucose

Lactase-glucose and galactase

Sucrase-glucose and fructose

Nucleic acid- nucleotides

Nuclease-nucleodtides

Lipids-small intestine

Fats-fatty acids

Lipase-fatty acids and glycerol

Hepatitis

Cirrhosis

Jaundice

Yellow skin discoloration due to excessive amounts of bile in blood

Various Causes- gallstone or diseased liver, hepatitis, tumor, etc.

If a gallstone blocks the common bile duct feces will be white and skin yellow

Gall stone

Blocks bile duct

Obstruction of common hepatic duct

Hepatitis or inflammation of liver

Usually due to to one of six hepatitis viruses

Nonviral causes include drug toxicity, and wile mushroom poisoning

In the U.S. 40% are due to HVB which is transmitted via blood transfusion, contaminated needles or sexual contact.

Is a chronic inflammation of the liver usually resulting from alcoholism or chronic hepatitis

Liver transplants are the only clinically proven effective treatment for patients with end-stage liver disease

The digestion of most macromolecules occur in the small intestine

Intestinal enzymes produced by brush-border cells further breakdown proteins and carbs into their monomers

Enzymes of SI

Peptidases

Sucrase

Lactase

Maltase

Intestinal lipase

Reduce peptides to amino acids

Reduces sucrose (cane sugar) to glucose and fructase

reduces lactose (milk sugar)

Reduces maltose to glucose

Reduces fats into fatty acids and glycerol

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Enzymes of Pancreas

Protease-protein

Trypsin, chymatrypsin, carboxypeptidase-protein

Lipase- lipids

HCI in stomach destroys amylase and stops carb digestion

Enzymes digest all 4 nutrients

Nuclease-nucleic acids

Sodium bicarbonate rich

Neutralizes

Mouth

Esophagus

Stomach

Small Intestine

Pancreas

Gall Bladder

Large Intestine

Rectum

Function

To receive food and begins mechanical digestion by mastication; chemical digestion also occurs

The oral cavity is the chamber between the palate and tongue

The narrow space between the teeth, cheeks, and lips is called the vestibule

Chews and lubricates food with saliva

Saliva contains enzymes that starts chemical digestion

Moves food (bolus) to pharynx

Anterior opening called oral orifice

Structure

Uvula

Floor

Roof

Formed by hard and soft palate

A downward projections of soft palate

Formed by tongue and its muscles

Lips

Keep food in mouth

Teeth

Breaks down food

Tongue

Muscle

Moves and mixes food with saliva (food+saliva= bolus)

Muscle

Cheeks

Form the lateral walls of the mouth and involved in expressions and chewing

Lips

Highly mobile structures that surround the mouth opening

Are sensitive to help judge the temperature and texture of foods.

Tongue

A thick, muscular organ covered by mucous membrane with taste buds within papillae; it is attached to the floor of the mouth by the lingual frenulum

The papillae also provide friction for moving food around in the mouth

Palate

Forms the roof of the oral cavity and has an anterior hard palate and posterior soft palate

The soft palate and uvula function to close off the nasal cavity during swallowing

Associated with the palate in the back of the mouth are palatine tonsils, which, because they are lymphatic tissue, help to protect the body against infection

Pharyngeal tonsils are located on the posterior wall of the pharynx, above the border of the soft palate

Teeth

Two sets of teeth develop in the sockets within the maxillary and mandibular bones

Through the actions of chewing, teeth breaking food into smaller pieces, beginning mechanical digestion

Each tooth consists of a crown and a root, and is made of enamel, dentin, pulp, cementum, nerves, and BV running through root canals

Teeth: incisors, cuspids, bicuspids, and molars

Incisors- cut

cuspids- tear and shred

bicuspid- crush and grind

Molars- crush and grind structures of a typical tooth

Salivary Glands

Secret saliva, which moistens and dissolves food particles, bind them, together, allows tasting, helps to cleanse the mouth and teeth, and begins carbohydrate digestion

Contain serous cells that produce a watery fluid with salivary amylase and mucous cells that produce lubrication and binding mucous

Receive parasympathetic stimulation that triggers the production of a large volume of saliva at the sigh or smell of food

Parotid glands

Submandibular Glands

lying in front of the ear are the largest of the major salivary glands, they secrete a clear, watery fluid (serous) rich in amylase

Located on the floor of the mouth, secret a more viscous fluid (serous and mucous)

Sublingual Glands

Inferior to the tongue, are the smallest of the major salivary glands and secrete a saliva that is thick and stringy (mucous)

Pharynx

Is a cavity lying behind the mouth

Structure

Connects the nasal and oral cavities with the larynx and esophagus

Is divided into the nasopharynx (top), oropharynx (middle), and largyngopharynx (bottom)

Function

Passageway for food and air from mouth to esophagus

Deglutition

Swallowing

Swallowing food passes from oropharynx into larngopharynx

Epiglottis (a flap of cartilage)

Closes so food goes into esophagus

Is a muscular tube leading to the stomach

A straight, collapsible, passageway leading to the stomach, through a diaphragm opening (esophageal hiatus)

Mucous glands are scattered throughout the submucosa of the esophagus and produce mucus to moisten and lubricate the inner lining of the tube

The lower esophageal (cardiae) sphincter helps to prevent regurgitation of the stomach contents into the esophagus

Function

Connects pharynx to stomach

Passageway only for food

Digestive function= propulsion

Moves food by peristalsis

Peristalsis-rhythmic wavelike contraction by musclaris layer of wall

Connects the stomach at lower esophageal sphincter

Circular ring of muscle

Sphincter can lead to acid reflex

Structure

J shaped, muscular organ, can hold about 1lt

Thick mucous membrane

Cardia and the Fundus

Body

Phyloric sphincter

enlarged opening next to esophagus (upper section; temporary storage

Cardiac sphincter seperates fundus from esophagus

Central main part

lower narrow section

Phyloric sphincter seperates pylorus from duodenum

Inside lined with rugae(gastric folds of the mucosa and submucosa)

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Function

3 layers of smooth muscle mix food into a tiny particle

Chemical digestion (mechanical-churning)

Glands secrete gastric juices: HCI, pepsin, intrinsic factor

HCI (secreted by Parietal cells) kills bacteria and denatures/digests proteins

Pepsin

Breaks peptide bonds in protein (secreted by Chief cells)

Intrinsic factor secreted by parietal cells, helps sm intestine absorb Vitamin B12

Mixing and holding chamber

Mucous cells produce mucus (protects stomach lining)

Forms chyme from food

Soupy mixture of macerated food and gastric juices

Food exits through Pyloric sphincter

Very little absorption

Small quantities of water and certain salts, alcohol, and some lipid soluble drugs.

Liver

Largest internal organ

Functions

Helps maintain concentration of blood glucose levels, metabolizes proteins, stores glycogen, iron, Vitamin A,D, B12

Responsible for many metabolic activities (carbohydrates, lipids, proteins)

Removes toxic substances from blood

Synthesizes lipoproteins, phospholipids, cholesterol

Converts carbohydrates and prtoeins to fat and breaks down amino acids, forming urea, to synthesize plasma proteins and clotting factors

Concert amino acids to other amino acids

Filters blood-removing damaged RBC's and foreign substances, removes toxins

Functions for digestion: secrete bile into duodenum

Bile

Water

Cholesterol, electrolytes, bile pigments and bile salts

Bile Salts

Emulsify (break up) fats

eliminates cholesterol

Bilirubin and Biliverden

Bile is a fat emulsifier, break up fats into smaller particles

Bile pigments are break down products from RBCs

Bile is secreted by hepatic cells

Have digestive function

Lack of bile salt can lead to poor lipid absorption and vitamin deficiencies

Stores excess bile for liver

Location: Under surface of liver

Connected to the cystic duct which joins to the hepatic duct-merge to common bile duct

Function

concentrations and stores bile produced in the liver, to release into small intestine (duodenum)

Location: Behind stomach, closely associated with small intestines

Function

Pancreatic juice (made by pancreatic acinar cells) into duodenum

Enzymes

Digest all 4 nutrients

Trypsin, chymotrypsin, carboxypeptidase-protein

Lipase-lipids

Protease-protein

Amylase- carbohydrates

Tube approx. 7m long, 2cm in diameter; fills most of the abdominal cavity; connects stomach to large intestine.

Functions

Mechanical digestion

Segmentation and peristalsis

Back and Forth movement

Mixes and breaks down chime (food+ gastric juices)

Chyme+secretions from pancreas and liver+ intestinal juices

Chemical Digestion

Intestinal glands secrete intestinal juices

Absorption

Of water and nutrients (90%)

Villi and Microvilli

Increase surface area for absorption

Lacteals

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Lymphatic capillaries; fat absorption into lymph

Sections

Duodenum

Most "fixed" in place

Chem. digestion

Liver-bile- fats

Pancrease-pancreatic juices

Carbs, proteins, and fats

Jejunum

Absorption

Circular folds to increase surface area

Ilium

Absorbs vitamins and bile salts

Ileocecal sphincter (valve) joins small intestine to large intestine cecum

1.5 m(5ft) long, wider diameter than sm. intes.

Separated from sm. intest. by ileocecal valve (sphincter

No villi present

Slow movement

Starts at ileocecal valve and ends at anus

Function

Gut Bacteria as E.coli live here

Digestion by bacteria

Synthesizes of Vitamin K, Vitamin B complex

Digestion of cellulose

Undigested food called fecal matter leaves the ileum and enters the cecum through the ileocecal shincter

Absorption of water and salt

Form, store, eliminate feces.

Bacteria ferment remaining carbs and release H, CO2 and Ch3 producing gas

Break down remaining proteins to amino acids

Decompose the bilirubin in bile to give feces their brown color

In a 24 hour period, feces are turned in stool in about 3-10 hours

Subdivisions

Sigmoid colon

Descending colon

Transverse colon

Bend called left colic fixture

Ascending colon

Bend called Right colic fixture

Right side

Retroperitoneal

Cecum

Pouch like area (site of appendix)

S shaped

Rectum

Near coccyx

Anal Canal (Anus)

Interior anal sphincter

Exterior anal sphincter

Appendix

Vermiform appendix-worm like structure ~9cm

Vestigial organ-noldeboted function

Near R hip bone

Contains lymphatic tissue

Attaches to cecum

3 in below ilececal valve

Many become inflamed resulting in appendicitis

Functions

Growth, blood coagulation, healing, diseases, digestion, reproduction, and many other functions.