The Human Digestive The Human Digestive SystemSystem

What is digestion?What is digestion?

The process of breaking down foods The process of breaking down foods into molecules the cells of the body into molecules the cells of the body can use.can use.

Where does digestion occur?Where does digestion occur?

The gastrointestinal tract (AKA- alimentary canal)Muscular tube approx. 9 meters long!

Organs of the Alimentary Canal Organs of the Alimentary Canal and their accessory organsand their accessory organs

Mechanical vs. Chemical Mechanical vs. Chemical DigestionDigestion

Mechanical Digestion= The physical Mechanical Digestion= The physical breakdown of food into smaller piecesbreakdown of food into smaller pieces

Chemical Digestion= Breaking the bonds Chemical Digestion= Breaking the bonds in food to change the chemical nature of itin food to change the chemical nature of it

Mouth Mouth (Buccal Cavity)(Buccal Cavity)

Mechanical Mechanical Digestion Digestion (mastication)(mastication)- - TeethTeeth break down break down foodfood- - TongueTongue manipulates manipulates food against the food against the hard hard palatepalate (bony roof of (bony roof of mouth) and contains mouth) and contains bumps (bumps (papillaepapillae) that ) that provide friction for provide friction for moving food around.moving food around.- The - The frenulumfrenulum connects the tongue to connects the tongue to the floor of the mouth.the floor of the mouth.

Mouth cont.Mouth cont. Chemical DigestionChemical Digestion

- Salivary glands that line the mouth produce saliva.- Salivary glands that line the mouth produce saliva.- Saliva moistens food particles, binds them together, - Saliva moistens food particles, binds them together, allows tasting, helps to cleanse the mouth and teeth, allows tasting, helps to cleanse the mouth and teeth, and begins carbohydrate digestion.and begins carbohydrate digestion.- - SalivaSaliva is a mixture of water, mucus and an enzyme is a mixture of water, mucus and an enzyme called called amylase (breaks down carbs)amylase (breaks down carbs)..- The mucus lubricates and holds the food together - The mucus lubricates and holds the food together forming a ball called a “forming a ball called a “bolusbolus”.”.

INTERESTING FACTINTERESTING FACT: : Halitosis results when food particles accumulate in the Halitosis results when food particles accumulate in the mouth and bacteria flourish. Saliva helps wash away mouth and bacteria flourish. Saliva helps wash away these food particles.these food particles.

ParotidParotid – – lateral lateral side of face, anterior side of face, anterior to ear – watery to ear – watery salivasaliva

SubmandibularSubmandibular – – floor of mouth floor of mouth SublingualSublingual – – inferior to tongue – inferior to tongue – thick salivathick saliva

1-1.5 L / day for digestion lubrication (swallowing) moistening (tasting)

Three pairs of Salivary GlandsThree pairs of Salivary GlandsThree pairs of Salivary GlandsThree pairs of Salivary Glands

PharynxPharynx The pharynx connects the nasal and oral The pharynx connects the nasal and oral

cavities with the larynx and esophagus cavities with the larynx and esophagus and is divided into a and is divided into a nasopharynxnasopharynx (top (top portion), portion), oropharynxoropharynx (middle portion), and (middle portion), and largyngopharynxlargyngopharynx (bottom portion). (bottom portion).

Sensory receptors in the pharynx sense Sensory receptors in the pharynx sense food, which triggers swallowing reflexes.food, which triggers swallowing reflexes.

EsophagusEsophagus When food is swallowed it passes When food is swallowed it passes

the pharynx and into the the pharynx and into the esophagus.esophagus.

The esophagus is a muscular tube The esophagus is a muscular tube approx. 10 inches long.approx. 10 inches long.

What type of muscle lines the What type of muscle lines the esophagus?esophagus?

Contractions and relaxations of Contractions and relaxations of these muscles move the bolus these muscles move the bolus down the esophagus. This process down the esophagus. This process is called- is called- PERISTALSISPERISTALSIS

Peristalsis is very effective= Can Peristalsis is very effective= Can drink upside downdrink upside down

Peristalsis

Cardiac SphincterCardiac Sphincter• Circular muscle that opens to allow food to pass from Circular muscle that opens to allow food to pass from

the esophagus into the stomach.the esophagus into the stomach.

• What if the cardiac sphincter doesn’t work properly?What if the cardiac sphincter doesn’t work properly?

Gastroesophageal reflux disease- GERD A condition in which the liquid content of the A condition in which the liquid content of the

stomach regurgitates (backs up or refluxes) into stomach regurgitates (backs up or refluxes) into the esophagus. The liquid can inflame and the esophagus. The liquid can inflame and damage the lining of the esophagus. The damage the lining of the esophagus. The regurgitated liquid usually contains acid and regurgitated liquid usually contains acid and pepsin that are produced by the stomach.pepsin that are produced by the stomach.

AchalasiaAchalasia

The term achalasia means "failure to The term achalasia means "failure to relax" and refers to the inability of the relax" and refers to the inability of the cardiac sphincter to open and let food cardiac sphincter to open and let food pass into the stomach. Also, the muscle pass into the stomach. Also, the muscle that lines the esophagus does not contract that lines the esophagus does not contract properly. As a result, patients with properly. As a result, patients with achalasia have difficulty in swallowing achalasia have difficulty in swallowing food.food.

StomachStomachThe stomach is divided into the cardiac, The stomach is divided into the cardiac,

fundus, body, and pylorus regions.fundus, body, and pylorus regions.

E

SIB

CF

P

PS

CS

StomachStomach• Mechanical Digestion in StomachMechanical Digestion in Stomach

- - The stomach is lined with smooth muscle. The stomach is lined with smooth muscle. This lining is folded and the folds are called This lining is folded and the folds are called rugaerugae. Smooth muscle of the stomach . Smooth muscle of the stomach twists and turns the stomach, physically twists and turns the stomach, physically breaking down food.breaking down food.- If the stomach is empty, then it growls. - If the stomach is empty, then it growls. This is due to the sounds made by the This is due to the sounds made by the contractions of the muscles.contractions of the muscles.

A Real Stomach!!!A Real Stomach!!!

Stomach cont.Stomach cont. Chemical DigestionChemical Digestion

- - Innermost lining of the stomach is a mucous Innermost lining of the stomach is a mucous membrane that has openings called membrane that has openings called gastric pitsgastric pits..- Gastric pits are the openings through which - Gastric pits are the openings through which secretions are released into the stomach.secretions are released into the stomach.- These secretions (called - These secretions (called gastric fluidgastric fluid) include: ) include: mucus, mucus, pepsinogenpepsinogen (breaks down proteins), and (breaks down proteins), and hydrochloric acid.hydrochloric acid.- The mucous coating of the stomach protects it - The mucous coating of the stomach protects it from the acid. If it breaks down = from the acid. If it breaks down = ULCER!!- Food usually stays in the stomach for 3-4 - Food usually stays in the stomach for 3-4 hours.hours.- The mixture produced from - The mixture produced from mechanical/chemical digestion is called mechanical/chemical digestion is called chymechyme (fats, sugars, vitamins, minerals, and proteins).(fats, sugars, vitamins, minerals, and proteins).

Small IntestineSmall Intestine Pyloric sphincterPyloric sphincter = Circular muscle that opens to allow = Circular muscle that opens to allow

chyme into the small intestine from the stomach. It allows chyme into the small intestine from the stomach. It allows approx. 5-15 ml in at a time.approx. 5-15 ml in at a time.

The lengthy small intestine receives secretions from the The lengthy small intestine receives secretions from the pancreas and liver. The small intestine functions to pancreas and liver. The small intestine functions to complete digestion of the nutrients in chyme, complete digestion of the nutrients in chyme, absorb the absorb the products of digestionproducts of digestion, and transport the remaining , and transport the remaining residues to the large intestine.residues to the large intestine.

If stretched out, the small intestine is 21 feet long! It is If stretched out, the small intestine is 21 feet long! It is held together by a thin tissue layer called held together by a thin tissue layer called mesenterymesentery..

The 3 parts of the small intestine include:The 3 parts of the small intestine include:11stst = = DuodenumDuodenum (10 inches) (10 inches)22ndnd= = JejunumJejunum (8 feet) (8 feet)33rdrd= = IIleumIIleum (13 feet) (13 feet)

Mesentery of Small Intestine:Mesentery of Small Intestine:

Liver and Gall BladderLiver and Gall Bladder LiverLiver

- Large brownnish-red organ to the right of the stomach- Large brownnish-red organ to the right of the stomach- Makes - Makes bilebile (important in fat digestion) (important in fat digestion)

Gall bladderGall bladder- Stores the bile made by the liver - Stores the bile made by the liver - Bile travels from the liver to the gall bladder through the - Bile travels from the liver to the gall bladder through the common hepatic duct and cystic duct.common hepatic duct and cystic duct.- When chyme is present in the small intestine - When chyme is present in the small intestine (duodenum), the gall bladder releases bile through the (duodenum), the gall bladder releases bile through the cystic duct to the cystic duct to the common bile duct common bile duct which dumps into the which dumps into the small intestine at the duodenum.small intestine at the duodenum.

Human Digestion: Small IntestineHuman Digestion: Small Intestine

Gall Bladder RemovalGall Bladder Removal

Why? Quick video of a removalQuick video of a removal

PancreasPancreas

The pancreas secretes The pancreas secretes pancreatic fluidpancreatic fluid into the small intestine (duodenum). This into the small intestine (duodenum). This helps breakdown the chyme.helps breakdown the chyme.

Pancreatic fluid leaves the pancreas Pancreatic fluid leaves the pancreas through the through the pancreatic ductpancreatic duct. The . The pancreatic duct joins the pancreatic duct joins the common bile ductcommon bile duct just before it enters the small intestine.just before it enters the small intestine.

Absorption in Absorption in the Small the Small IntestineIntestine

Digestion products are absorbed into the circulatory Digestion products are absorbed into the circulatory system through blood and lymph vessels.system through blood and lymph vessels.

The lining of the jejunum and illeum has extensions The lining of the jejunum and illeum has extensions called called villi villi that increase surface area.that increase surface area.

Inside the villi are capillaries and lacteal (lymph Inside the villi are capillaries and lacteal (lymph vessels).vessels).

Fatty acids enter lactealsFatty acids enter lacteals Other substances diffuse into capillaries and carried to Other substances diffuse into capillaries and carried to

cells of the bodycells of the body

Celiac DiseaseCeliac Disease

Celiac disease is when the small intestine lining (villi) is damaged and absorption of nutrients is hindered.

The damage is due to a reaction to eating gluten, which is found in wheat, barley, rye, and possibly oats.

The immune system incorrectly attacks villi because of the gluten they are absorbing.

Large IntestineLarge Intestine Once the remaining food enters the large intestine, Once the remaining food enters the large intestine,

it moves toward the anus by contractions of the it moves toward the anus by contractions of the smooth muscle in the lining of the large intestine.smooth muscle in the lining of the large intestine.

The large intestine consists of the cecum (pouch The large intestine consists of the cecum (pouch at the beginning of the large intestine), colon at the beginning of the large intestine), colon (ascending, transverse, descending, and sigmoid (ascending, transverse, descending, and sigmoid regions), the rectum, and the anal canal.regions), the rectum, and the anal canal.

As the matter moves through the large intestine, As the matter moves through the large intestine, water is absorbed into the capillaries in the lining. water is absorbed into the capillaries in the lining. This makes the matter more solid.This makes the matter more solid.

The solid material is called The solid material is called fecesfeces..

Large IntestineLarge Intestine

What is Feces??What is Feces??

Feces is composed of undigested material, Feces is composed of undigested material, water, electrolytes, mucus, and bacteria.water, electrolytes, mucus, and bacteria.

The color of feces is due to the action of The color of feces is due to the action of bacteria on bile pigments.bacteria on bile pigments.

The odor of feces is due to the action of The odor of feces is due to the action of bacteria.bacteria.

What can we learn from our poop? Color, What can we learn from our poop? Color, smell, consistency, curvature?smell, consistency, curvature?

What goes in must come out!What goes in must come out!

DiverticulitisDiverticulitis Diverticulosis happens when pouches (diverticula ) form in the Diverticulosis happens when pouches (diverticula ) form in the

wall of the colon . If these pouches get inflamed or infected wall of the colon . If these pouches get inflamed or infected (with feces), it is called diverticulitis. Diverticulitis can be very (with feces), it is called diverticulitis. Diverticulitis can be very painful.painful.

Doctors aren't sure what causes diverticula in the colon. They Doctors aren't sure what causes diverticula in the colon. They think that a low-fiber diet may play a role. Without fiber to add think that a low-fiber diet may play a role. Without fiber to add bulk to the stool, the colon has to work harder than normal to bulk to the stool, the colon has to work harder than normal to push the stool forward. The pressure from this may cause push the stool forward. The pressure from this may cause pouches to form in weak spots along the colon.pouches to form in weak spots along the colon.

Diverticulitis happens when feces get trapped in the pouches Diverticulitis happens when feces get trapped in the pouches (diverticula). This allows bacteria to grow in the pouches. This (diverticula). This allows bacteria to grow in the pouches. This can lead to inflammation or infection.can lead to inflammation or infection.

Facts at a GlanceFacts at a Glance

The average person eats 3 pounds of food The average person eats 3 pounds of food a day. That's 1,095 pounds a year! a day. That's 1,095 pounds a year!

An adult stomach holds 5 cups. An adult stomach holds 5 cups. 35 million glands produce acid in the 35 million glands produce acid in the

stomach. The acid can dissolve a razor stomach. The acid can dissolve a razor blade in one week! blade in one week!

The body uses energy efficiently. (900 The body uses energy efficiently. (900 miles to the gallon!) miles to the gallon!)

Our own food breakdown factory!Our own food breakdown factory!

Why do we need our urinary Why do we need our urinary system?system?

• To remove (excrete) metabolic waste To remove (excrete) metabolic waste from the bloodstream and carry it out of from the bloodstream and carry it out of the body in the form of urinethe body in the form of urine

– Metabolism: Cells breaking down Metabolism: Cells breaking down compounds for energycompounds for energy

• To regulate the water content in the To regulate the water content in the bodybody

Functions of the organs of the human urinary system

Kidneys- Where blood is filtered and urine is produced

Ureter- Narrow tube connected to each kidney that carries urine to the urinary bladder

Urinary bladder- A muscular sac that stores urine and contracts to release urine

Urethra- The tube that carries urine from the bladder out of the body

Organs of the human urinary system

Kidney

Renal artery

Ureter

Renal vein

Urinary bladder

Urethra