Joe CristofanoBilly Sieff

Digestive System

Cnidarian Digestive system• Cnidarians have a unique digestive cavity

called the Gastrovascular cavity.• The two body plans for cnidaria are Polyps

and Medusa.

Cnidarian Digestive system• The gastrovascular cavity has only one

opening which functions as both a mouth and an anus.

• The gastrovascular cavity is responsible for not just digestion but also the distribution of the nutrients being digested.

Cnidarian Digestive systemHydra, a carnivorous Cnidarian is a good

example.• It uses its tentacles to shove its prey through

its mouth into the gastrovascular cavity.• Then the Gastrodermis(the inside layer of

its epidermis) will release digestive enzymes into the cavity.

• The enzymes break down soft tissue of the prey and then other specialized cells in the gastrodermis will engulf the food particles.

Cnidarian Digestive system• All undigested materials remaining in the

gastrodermis and then released out of the singular opening.

Cnidarian advantages and adaptations• Cnidaria are not very complex organisms

and it makes for a simple life.• The tentacles make it easy to pull in prey

and due to the simple body plan, they have a gastrovascular cavity, and the lining of it distributes the nutrients directly to the necessary parts of the organism.

Annelida Digestive Tract• In typical annelids such as earthworms and

flatworms, the alimentary canal usually includes a muscular pharynx whose purpose is to draw food into the mouth.

Annelida Digestive Tract• Food then moves through the esophagus

down into the crop, a compartment used for storing and moistening food.

• food moves from the crop to the gizzard. This is where mechanical digestion takes place.

• The muscular gizzard crushes and breaks down food, often with the aid of small grains of gravel and sand previously ingested.

Annelida Digestive Tract• Further digestion and absorption continues

to take place in the intestine. Waste productions are then excreted through the anus.

Annelida Digestive Adaptation

• One adaptation in most annelids (especially earthworms and flatworms) is their muscular gizzards, whose thick,tough, rigid walls of muscle allow them to keep particles of sand and gravel within their gizzards for extended periods of time to allow for further breakdown of food.

• This is an imperative adaptation for invertebrates who spend most of their time on or underneath the ground.

Arthropod Digestive Tract• Arthropod digestive systems are

normally composed of 3 general sections of several digestive chambers, the foregut, midgut, and hindgut.

Arthropod Digestive Tract• The foregut is composed of the

esophagus and the crop. • The midgut is primarily made of

gastric cecae, which are pouches that extend from the beginning of the midgut and play large roles in absorption and digestion.

• The hindgut is comprised of a rectum and an anus.

Arthropod Digestive Tract

Arthopod Adaptations• Multiple pouches of gastric cecae allow for

large amounts of food to be processed and digested simultaneously.

• Multiple sections for the digestive tract within the foregut, midgut, and hindgut allow for more space for the crop, gastric cecae, and gizzards.

Mammalian Digestion• Most animals have an

Alimentary Canal (digestive tract or tube with a separate entrance and exit)

• Mammalian digestive system consists of an alimentary canal and accessory glands to release digestive fluids into the canal via ducts.

Digestive Pathway• In order for food particles and nutrients to

travel through the alimentary canal, peristalsis must occur.

• Peristalsis is the alternating, wave-like contraction/relaxation of the smooth muscle in the digestive tract. This action pushes the nutrients through the tract.

Digestive Pathway• Sphincters are valves found the

junctions between compartments that act like clamps or drawstrings, closing and opening to allow food particles to pass or not pass.

• With the human digestive system as an example, the initial step of the process is the entrance through the oral cavity.

Oral Cavity• Teeth in the mouth mash, grind and break

down food into smaller chunks.• Salivary glands are stimulated by the

presence of food and they release saliva into the oral cavity through ducts.

• Saliva starts the process of breaking down the food while it also protects the oral cavity.

• 3 pairs of salivary glands

Saliva• Amylase is the enzyme found in saliva.• It hydrolyzes starch & glycogen into smaller

polysaccharides and maltose ( a disaccharide).• Mucus is responsible for most of the protective

effect.• it is a mixture of water, salts, cells and slippery

glycoproteins, these make it very viscous.• Mucus mainly protects the lining of the oral

cavity from abrasion and it also is a lubricant for food traveling through the tract.

Beginning of Digestive Tract• The tongue is vital for digestion, because is

decides what needs to be digested and what doesn't.

• The tongue also pushes food down into the Pharynx or throat.

• When moving the food towards the pharynx, the tongue molds the food into a Bolus (ball shape)

• The tongue aids in pushing downward during swallowing and official entering the Pharynx.

Digestive Tract• At the bottom of the Pharynx there are 2

openings to the Larynx (wind-pipe) and the esophagus ( connects to stomach).

• The Epiglottis is a flap of cartilage that will flip up or down covering up either the Larynx or Esophagus in order for breathing or swallowing food.

• swallowing directs the bolus into the esophagus, and if it fails the food one is currently digesting could reach the Trachea, hense choking occurs.

Stomach• The stomach is where food is stored and

begins digestion of proteins.• Due to the elasticity of the lining of the

stomach, it can hold up to about 2 L of food/drink on average.

• Gastric Juice is secreted by the stomach mixes with the food while it is being churned, the mixture is called Chyme.

• Gastric glands in the stomach produce the gastric juice

Stomach• Two components of gastric juices catalyze

chemical digestion.• One of which is Hydrochloric Acid (HCl• HCl has a very low pH,making it acidic

enough to dissolve iron nails!• The second is pepsin, a protease (protein

digesting enzyme).

Stomach• Parietal cells secrete hydrogen and chloride

ions to create HCl.

• Chief cells release inactive pepsin into the lumen. This inactive pepsin is known as pepsinogen.

Small Intestine• Most of the enzymatic hydrolysis that of the

macromolecules from food happens in the Small Intestine.

• In humans, it is over 20 feet long.• The first 10 inches is the Duodenum, where

Chyme mixes with digestive fluids that are secreted from the pancreas liver and gallbladder and even from cells in the small intestinal wall.

Pancreas,Liver and Gallbladder• The Pancreas produces an Alkaline solution,

which is rich in bicarbonate, and many other enzymes.

• This neutralizes the Chymes acidity• The liver produces Bile (contains bile salts

that aid in absorption and digestion of lipids), which is vital for digesting fats and other lipids.

• The epithelial tissue that lines the duodenum secrets many digestive enzymes.

Large Intestine• The last organ in the Digestive Tract is the

Large Intestine• it is made up of the colon, cecum and rectum

Large Intestine• The cecum is pouch important for fermenting

ingested materials.o more important in animals that eat alot of

plants.• The Colon leads to the rectum and the anus• The Appendix is removable due to its very small

role in immunity.• colon is mainly meant to recover water that

entered the tract as a solvent of digestive juices.

• Feces is the waste, before it reaches that point the material takes about 12-24 hours to travel through the colon alone.

Mammalian adaptation and advantages• The length of the digestive tract directly

correlates with the diet of the species.o for example, omnivores and herbivores have longer

tracts because vegetation is harder to digest do to cell walls and cellulose.

• Animals do not contain enzymes to digest cellulose, so bacteria is present in the digestive system to carry out that function.o The microorganisms contain the necessary enzymes

to digest the cellulose into simple sugars and other consumeable materials.

Mammalian adaptation and advantages• Out of all of the herbivorous diets, the

ruminants have the most elaborate adaptations.

• The ruminant digestive tract has four main chambers.

• The diet that ruminants absorb their nutrients ends up being much richer than the grass that it eats.o Ruminants actually get most of their nutrients by

digesting the mutualistic microorganisms, this is allowed because of the high reproduction rate of the microorganisms.

Why is it Important?• Digestion is very important to breaking down

the products of food into usable forms, such as energy and cellular components.

• Also the food needs to be broken down into a reasonable size for consumption without rupturing organs.

• also upon breaking down food it makes thing more easily digested by increasing surface area thus decreasing time needed to digest, making it much more efficient.

Interdependence with other systems• One of the main interdependencies is how in

order for a bolus of food to travel through the esophagus, contractions and relaxations must occur.o smooth muscle is responsible for this, and the

muscular system is responsible for this.

• Another very important interdependence is with the endocrine system because it is responsible for the glands that secrete fluids and enzymes vital to digestion.

Interdependence• The circulatory system is very dependant on

the digestive system because it delivers nutrients to the blood stream.o By digesting food and getting the nutrients sent to

the blood stream, it allows the nutrients to be distributed throughout the body to the desired locations.

Digestive Diseases in Humans

• One major digestive disease that affects humans is known as Celiac's Disease.

• This disease can cause damage to the small intestine which prevents it from absorption of nutrients.

• The exact cause of celiac disease is unknown. The lining of human is full of villi which help absorb nutrients. When people with celiac disease eat foods or use products that contain gluten, their immune system reacts by damaging these villi.

Celiac's Disease• Symptoms include: lactose intolerance,

abdominal pain, decreased appetite, diarrhea, and unexplained weight loss.

• Unfortunately, Celiac's Disease cannot be cured. However, symptoms can be avoided and the lining of the small and large intestine can be healed if that person remains on a lifelong gluten-free diet.

Crohn's Disease• Like Celiac's Disease, the cause of Crohn's

Disease is unknown. It is an autoimmune disorder in which the body's immune system mistakenly attacks the body's healthy body tissue.

• Symptoms include: crampy abdominal pain, fever, fatigue, and pain with passing stool.

• Though there are no cures for this disease, it can be managed with proper diets and low levels of stress.