Essential Question What are the structures of the digestive system? 2.07 Remember the structures of the digestive system2.

Essential Question

What are the structures of the digestive system?

2.07 Remember the structures of the digestive system 2

Structures of the digestive system

Digestive system Also known as:

Alimentary Canal Digestive Tract Gastrointestinal Tract

Upper GI Lower GI

Approximately 30’ in length from mouth to anus


Primary structures Mouth Esophagus Stomach Small intestines Large intestines

Accessory structures Tongue Teeth Salivary glands Pancreas Liver Gall bladder




Mouth (buccal cavity)

Tongue Teeth Salivary Glands Palate Uvula



Tongue Attached to floor of

mouth Made of skeletal

muscle attached to four bones

Taste buds on the surface Sweet Sour Bitter Salty



Teeth Primary (deciduous)

20 “baby teeth” Secondary

(permanent) 32 “adult teeth”


Deciduous Teeth: baby’s first teeth which eventually fall outAll deciduous teeth are in place by 2 ½ years.Between 6 and 12 years, deciduous teeth begin to fall out and are replaced by 32 larger permanent teeth

TYPES OF TEETH1.Incisors: located at the front of the mouth, they are blade sharp and are

used to cut food 2. Canine teeth: located next to incisors, used for holding, tearing or slashing food 3. Bicuspids, or premolars: crush and grind food 4. Molars: Located in the very back of the mouth, have flattened tops, crush and grind food.

Structure of Teeth•All teeth have a cow, neck and root•Crown: The visible portion of the tooth covered by enamel (which is the hardest biologically manufactured substance)•Neck is the transitional section that leads to the root•Root: the portion of the tooth that anchors it to its bony socket. It’s held in place by fibers.•MOST Teeth are made up of dentin, a mineralized bone like substance.•Inside teeth there’s a layer of connective tissue called pulp located inside the pulp cavity.


Salivary glands Parotid glands: located anterior and

inferior to each ear. Swell when you get

mumps Largest salivary gland

Submandibular gland located along the inner

surface of the lower jaw Sublingual gland


Salivary glands produce 1-1.5 liters of saliva daily.Small amounts are continuously secreted to keep the mouth moist.Saliva is 99.4% water and contains antibodies, buffers, ions, waste products and enzymesFunction of saliva: Contains enzymes that begin the chemical breakdown of foodAfter eating, saliva cleans the oral surfaces, reducing the amount of bacteria that grow in the mouth


Palate Hard Soft

Uvula Flap of skin

hanging in the

back of the throat

Aids in swallowing by directing food toward the pharnyx


Structures of the digestive system Pharynx (throat)

Nasopharynx Connects to the nose Oropharynx Connects to the mouth Located at the back of the Tongue Laryngopharynx A passageway for food, Water, and air into the Internal parts of the body.

]2.07 Remember the structures of the

digestive system 12


Esophagus Muscular tube, 10” long Transports food from

the pharynx to the stomach

Is a collapsed tube until a bolus of food is eaten.

Esophageal wall layers– Mucosa– Submucosa– Muscular– External serous

2.07 Remember the structures of the

digestive system 13

• 4 layers make up the alimentary tract• Mucosa: innermost layer, lines the canal, contains cells

that secrete enzymes to break down food, contains goblet cells that secrete mucus for lubrication

• Submucosa: the next layer • Composed of soft connective tissue• Contains blood vessels, lymph vessels, lymph nodes and

nerve endings.• Musculara Externa the next layer• Innermost layer of muscle encircles the canal• Outer most layer is longitudinal so it lies in the direction of

the canal• Serosa: the outermost layer makes up visceral

peritoneum• Peritoneum is a serous membrane in the abdominopelvic

cavity. It has two layers:

At the end of the esophagus is a muscular “Door” called the lower esophageal sphincter . The LES is also known as the cardiac sphincter.It must open to allow food to move into the stomachAfter food passes through, it must close to prevent stomach acids from splashing back up into the esophagus.If the sphincter opens, it will cause heartburn (pyrosis)


Stomach Upper left quadrant of

the of the abdominal cavity

Fundus Body Pylorus

Cardiac Sphincter Pyloric Sphincter Rugae,


STOMACH FUNCTIONS:

•Serves as a temporary holding area for received food•Secretes gastric acids and enzymes that mix with food, performing chemical digestion•Regulates the rate partially digested food (chyme) enters the intestines•Absorbs small amounts of water on a limited basis•It takes about 4 hours for the stomach to empty following a meal.•Liquids and CHO’s pass through quickly•Proteins take more time•Fats take the longest usually between 4-6 hours


Accessories… Pancreas

6-9 inches longLocated behind the stomachExtending from duodenum to the spleenIt secretes buffers to neutralize the acids in the chyme saving the intestinal walls from damageReleases enzymes that break down sugars and starches, breaks down fats and proteins


GallbladderSac shaped organ, 3-4 inches longLocated under the liver’s right lobeIt stores bile produced by the liver

If the bile becomes over concentrated, bile salts may solidify forming gallstones

Fatty foods in the duodenum (first section of small intestines)

Cause the gallbladder to contract releasing bile into the common bile duct and this

leads to the duodenum.

LiverLocated in front of the diaphragm

(anterior)Weighs 3.3pounds

Is the largest glandular organ in the bodyLargest organ in the abdomen

Is divided into a large right lobe and a smaller left lobe.

Receives about 1 ½ quarts of blood every minute from the hepatic portal vein

And hepatic artery.The blood provides oxygen rich blood that

keeps the liver tissue alive

FUNCTIONS OF THE LIVERCreates body heat

Detoxifies the body of harmful substances such as certain drugs and alcohols

Destroys old blood cells and recycles their usable partsThe pigment from bilirubin is a waste product and is eliminated in bile

giving feces its distinctive colorForms blood plasma proteins such as albumin and globulins

Produces clotting proteins: fibrinogen and prothrombinManufactures bile, needed for the digestion of fats

Stores and modifies fats for more efficient use by the body’s cellsSynthesizes urea, a by product of protein metabolism, so it can be

eliminated by the bodyStores sugars (when our blood sugar levels fall below normal, the

liver releases glucose into the blood streamStores vitamins A, B12, D, E, and K

Makes cholesterol


Large intestines Approximately 2” in

diameter 5’ long Begin at the junction of

the ileum (last portion of small intestine) and extends to the anus


Large Intestines are approximately 5 feet long and 25 inches in diameter

FUNCTIONWater absorption

Absorption of vitamins produced by the health bacteria in the large intestine

Compaction of waste products for eliminationLarge intestines contain no villi, so little nutrient

absorption occurs here.

Three Main Regions of Large Intestines Cecum pouch shaped structure that receives any

undigested food and water from the ileumThe appendix is attached to the cecum

The appendix is a 3 “ long, slender hollow, dead ended tube lined with lymphatic tissueThe appendix has no current purpose

If it becomes blocked or inflamed it causes appendicitis

Colon has 4 secions: ascending colon, transverse colon, descending colon, and sigmoid colon(the S shape portion that extends from the left side to the rectum

RECTUMOpens to the anal

canal/anusAnal sphincter opens and

closes to allow the passage of solid waste(feces) from the colon to the outside

world

Essential Question

What are the structures of the digestive system?


Essential Question What are the structures of the digestive system? 2.07 Remember the structures of the digestive system2.

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