DIGESTIVE SYSTEM

DIGESTIVE DIGESTIVE SYSTEMSYSTEM

IntroductionIntroduction• concerned with the function of nutrition which includes

ingestion, digestion, absorption and egestion• process of digestion involves the physical and chemical

breakdown of food to render it soluble and ready for reabsorption

• tongue and teeth help in mechanical breakdown of food• chemical digestion occurs with help of digestive juices

containing enzymes secreted by the digestive glands• secretion of enzymes is basically under the control of

hormones• passage of food along the digestive tract is aided by gut

motility controlled by nervous system

Incomplete TypeIncomplete Type• when anus is absent, mouth serves for ingestion of food and

egestion of waste materials

Fasciola or Clonorchis Parts:• mouth – anterior end• oral sucker – circular and muscular sucking disc

surrounding the mouth• pharynx – short muscle• esophagus – short tube from the pharynx

additional for Fasciola• side branches or diverticula of the intestines are very

prominent and seem to fill the body

COMPLETE TYPECOMPLETE TYPE

• mouth and anus are present

• may be subdivided into the digestive tract, the digestive glands, and the accessory structures

Coelom, Peritoneum, and Coelom, Peritoneum, and MesenteriesMesenteries

Coelom • – cavity containg the visceral organs

divided into:a. small pericardial cavity – contains the heartb. larger pleuro-peritoneal cavity – which contains the rest of the visceral organs

Peritoneum – connective tissue membrane that lines the coelom

Types:a. parietal peritoneum – lines the body wallb. visceral peritoneum – covers most visceral organs

Coelom, Peritoneum, and Coelom, Peritoneum, and MesenteriesMesenteries

Mesenteries • two layers of the peritoneum that suspends viscera

from the dorsal body wall• name of organ they suspend

Omentum• double membrane continuous with the mesenteries

that connect the visceral organs with one another• also named after organ they connect

Buccal CavityBuccal Cavity- large cavity exposed upon opening the mouth

Parts:• maxillary teeth – in the upper jaw • sticky tongue – located at the floor of the cavity which captures

food and passes it on the esophageal opening• glottis – slit-like opening to the respiratory system and is found at

the region between the tongue and esophageal opening• vocal sacs – where pair of slits lead to ; slits are located lateral to

the glottis and near angle of jaw• choanae or internal nares- pair of holes at the roof of the buccal

cavity • vomerine teeth- pair of v-shaped formations at the root of the

mouth• Eustachian tube – opening or recess near the angle

1. Vomerine Teeth

2. Internal Nares

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3. Opening to the Eustachian Tube

4. Maxillary Teeth

Digestive TubeDigestive Tube1. esophagus

– short tube connecting the oral cavity to the stomach2. Stomach

– bag shaped muscle Parts of stomach:a. cardiac end – anterior portion continuous with the esophagusb. pyloric end – posterior portion continuous with the small intestinec. greater curvature – outer curvatured. lesser curvature – inner curvaturee. rugae – lines of the inner wall of the stomach

3. pyloric sphincter – constriction at the junction of the stomach and the small intestine

Digestive TubeDigestive Tube4. Small Intestine

- digestive tube that has become the long coiled structure from the pylorus- where most chemical digestion and absorption occurs

Has 2 regions:a. duodenum – bends anteriorly from the pylorus and runs parallel to the stomachb. ileum – longer and posterior

5. Large Intestine- where digestive tube enlarges- further breakdown of undigested material by bacterial action and

the absorption of water occur here

Digestive TubeDigestive Tube6. Cloaca

– short narrow tube which opens to the outside through the anus- urine and gametes also pass through the cloaca and anus

Mesenteries found in digestive system• dorsal mesentery – digestive tube is suspended from the

dorsal body• mesogaster – mesenteries in the stomach at its cardiac end• mesentery proper or mesenterium – suspends the ileum• mesorectum – suspends rectum

7. Spleen – dark lymphoid organ lying within the fold of the mesorectum

Parts of the Digestive System

3. Spleen

4. Liver

5. Stomach

6. Small Intestine

7. Large Intestine

RESPIRATORY RESPIRATORY SYSTEMSYSTEM

Types of Respiratory OrgansTypes of Respiratory Organs

1. gills - aquatic animals

2. lungs – evaginations (outpocketings )of the digestive tube for terrestrial animals

3. tracheal system – invaginations of the integument (inpocketings)

TYPES OF TYPES OF RESPIRATORY RESPIRATORY

SYSTEMSYSTEM

AQUATIC RESPIRATORY SYSTEMSAQUATIC RESPIRATORY SYSTEMS

Gills of Fishes-are delicate comb-like structures

a. Operculum – covers the gillsb. Gill chamber – part of the pharynxc. Gill arches – bony structures where gills are arched d. Gill filaments – arranged in parallel rows in rich in blood capillaries, this

also gives the dark red color of the gills in live or fresh specimene. Pharyngeal clefts- wide slits between the gill arches which serve for the

passage of water from the pharynx to the gill chamber

Breathing Movements of Fishes• water is taken in through the mouth and made to pass through the

gills then expelled out of the gill chamber through the gill aperture

TERRESTIAL RESPIRATORY TERRESTIAL RESPIRATORY SYSTEMSSYSTEMS

Tracheal System of Insects• respiratory organs consists of a branching

system of air tubes which supplies oxygen directly to the tissues

Parts• tracheal trunk – short segmental branches

that lead outside to spiracles and in fine branches, the tracheoles, connected directly to the tissues

• spiracles – where exchange of gases occur

TERRESTIAL RESPIRATORY TERRESTIAL RESPIRATORY SYSTEMSSYSTEMS

Lung System of Vertebrates

Parts• glottis – median slit, posterior to the tongue which leads to

the larynx• arytenoids – pair of cartilages on both sides of the glottis

which is covered by mucous• cricoid cartilage – ring shaped cartilage that borders

arytenoids• vocal cords – a pair of elastic, thread-like bands• lungs – pair of spongy sacs where larynx leads to

Excretory SystemExcretory System

Frog’s Excretory SystemFrog’s Excretory SystemKidney flat, ovoid reddish organs lying in a space retroperitoneal adrenals maybe observed as the yellowish streaks on the

ventral surfaceCisterna Magna space between the muscles of the dorsal body wall and

the peritoneumMesonephric or Wollfian Duct thread like tubular structure on the lateral side of each

kidney continues posteriorly beyond the kidney and enters the

cloaca separately on its dorsal wallUrinary Bladder connected to the ventral wall of the cloaca which serves

as storage of urine

Parts of the Excretory System

8. Kidney

9. Urinary Bladder

Mammalian KidneyMammalian KidneyKidney substance is easily divisible into two regions:• outer cortex

- contains the microscopic renal corpuscles and tubules• inner medulla

- contains collecting tubules that open at the renal papilla

Renal Pelvis - where renal papilla opens- expanded beginning in the ureter or metanephric duct

Metanephric Duct – leads tourinary bladder

Ureter – closely associated with blood vessels

• * all are found in a concavity called the hilus

CIRCULATORY SYSTEMCIRCULATORY SYSTEM

Function of the Circulatory SystemFunction of the Circulatory System

• Responsible for the transport of gases, nutrients, metabolic wastes, hormones and other substances in the different parts of the body.

• It assists in maintaining constancy of the internal environment (homeostasis) of the organism

OPEN SYSTEMOPEN SYSTEM• Heart

– Pericardial sinus cavity where the heart lies; open at the posterior end

– Dorsal Diaphragm membrane forming the ventral wall of the pericardial sinus

– Aorta vessel from the anterior end of the heart, which opens into the sinuses of the head

– Composed of a series of chambers

– Ostia: paired lateral openings at the posterior end of each chamber which are guarded by valves

Path of BloodPath of Blood• Colorless blood from the pericardial sinus enters

each chamber thru these openings.

• Blood is kept in circulation by the rhythmic contraction of the chambers of the heart from the posterior to the anterior chambers of the aorta

• Blood then permeates into the different parts of the body and finally returns to the pericardial sinus through the posterior opening.

CLOSED SYSTEMCLOSED SYSTEMBlood Vascular System

Composed of:a. Bloodb. Heart

- pumping action of the heart creates pressure that drives - the blood to the different parts of the body

c. Arteries- conveys blood from the heart to the different parts of the body

d. Veins- convey blood back to the heart

e. Capillaries- connect arterioles with the venulesArterioles small arteriesVenules small veins

Lymphatic SystemLymphatic SystemComposed of:

– Lymph vessels– Lymph spaces– Lymph circulating fluid

Where is it located?Dorso-lateral subcutaneous connective tissue

Tissue connecting the skin to the body wallDorsal subcutaneous lymph space

space between the skin and the dorsal body wall where lymph is pumped into veins by lymph hearts

Lymph Hearts Contractile hearts found between the third vertebra and the posterior corners of the suprascapula

Anterior Abdominal Vein underneath the linea alba

HEARTHEARTa. Pericardial cavity

where the heart lies separated from the pleuroperitoneal cavity by the transverse septum

b. Parietal pericardium (pericardial sac) lining of the heart which continues as the visceral pericardium

c. Visceral pericardiumd. Transverse Septum

Separates the pericardial cavity and the pleuroperitoneal cavity

e. Pleuroperitoneal Cavity contains the visceral organs (minus the heart)

CHAMBERS OF THE HEARTCHAMBERS OF THE HEARTSinus venosus

Dark colored triangular structure, connected to the ventral wall of the right atrium

Left and Right atria anterior, thin walled

Ventricle posterior, thick walled

Conus arteriosus bulb like, lies obliquely on the dorsal wall of the right atrium base of all the arteriesarises from the antero-ventral side of the ventricle

* Contraction Systole* Relaxation Diastole

Ventral Aspect• Ventricle

• Right Atrium

• Left Atrium

• Conus Arteriosus

• Truncus Arteriosus

• Pulmocutaneous Artery

• Systemic Artery

• Common Carotid Artery

Dorsal Aspect1. Ventricle

2. Right Atrium

3. Left Atrium

4. Sinus Venosus

5. Pulmonary Vein

6. Pulmocutaneous Arches

7. Systemic Arches

8. Common Carotid Arches

VENOUS SYSTEMVENOUS SYSTEMPrincipal Divisions

Systemic carry unoxygenated blood from the different parts of the body directly to the right atrium

Portal carry unoxygenated blood through a system of blood capillaries in the liver or kidney from where the blood is recollected by systemic veins to be brought back to the right atrium of the heart

Pulmonary carry oxygenated blood from the lungs directly to the left atrium

VEINSVEINSLeft/Right Precaval veins

a.k.a. anterior vena cava big blood vessels entering the Sinus venosus antero-lateral angles

Postcaval vein a.k.a. posterior vena cava

Veins connected to the Anterior vena cavaa. External jugular vein

anteriorb. Innominate veinc. Subclavian vein

Brachial vein Musculocutaneous vein

PORTAL VEINSPORTAL VEINSHepatic Portal SystemConsist of the:a. Hepatic portal vein

drains blood from the following tributariesgastric vein from the stomachsplenic vein from the spleenpancreatic vein from the pancreasintestinal veins from the small intestinesVentral abdominal vein

brings the drained blood to the liver

b. Hepatic vein

Renal Portal SystemConsist of the:a. Renal portal vein

lies on the lateral margin of the kidney alongside the mesonephric duct

b. Veins that drain from the dorsal body wallc. Oviduct (for females)d. Femoral vein

anterior and dorsal sides of the thigh and the rest of the hindlimbe. Pelvic vein

medial branch of the femoral vein before joining the renal portal vein

course along the posterior abdominal wall, where they receive short veins from the urinary bladder, and then

unite ventrally to form the anterior abdominal veinf. Sciatic vein

posterior side of the thigh

PORTAL VEINSPORTAL VEINS

Pulmonary VeinsPulmonary Veins

from the lungs they enter the left atrium

ARTERIAL SYSTEMARTERIAL SYSTEM

Arteries thick-walled, light colored, generally deeply

set in the bodyblood flow is pulsating or in spurtscarry oxygenated blood (minus the

pulmonary artery)

ARTERIAL SYSTEMARTERIAL SYSTEMVentral Side of the Heart

Conus arteriosus arises from the right antero ventral side of the ventricle serves as the base of all arteries

Truncus arteriosus anterior of the conus arteriosus immediately divides into the left and right trunks

Arteries connected to the Truncus Arteries connected to the Truncus arteriosusarteriosus

Common carotid artery anterior branch divides into two branches:Internal carotid artery

carotid gland round yellowish gland located near the base

External carotid artery

Systemic artery middle branch arches dorsally and posteriorly gives small branches to the:

Larynx, muscles of the jaw, dorsal side of the esophagus, orbit, nose, vertebral column

Pulmocutaneous Artery

Branches of Systemic ArteryBranches of Systemic ArterySubclavian artery

supplies the shoulder and neighboring parts brachial artery: subclavian artery that continues to the forearm

Pulmocutaneous artery posterior

Dorsal Aorta posterior continuation of the unified left and right systemic arches

Coeliaco-mesenteric artery arising ventrally at the junction of the systemic arches and dorsal aorta divides into the:

coeliac arteryanterior mesenteric artery

Branches of Systemic ArteryBranches of Systemic ArteryPosterior mesenteric artery

unpaired artery near the posterior end of the aorta, arising from its ventral side

Left/Right common Iliac arteries the split of the posterior end of the aorta

Femoral artery small dorsally directed artery posterior to the common iliac supplies blood to the skin and muscles of the anterior part of the thigh

Sciatic artery common iliac artery that proceeds to the rest of the hindlimb

Internal Structure of the Frog’s Internal Structure of the Frog’s Heart and It’s BranchesHeart and It’s Branches

a. Right Atrium larger thin walled chamber of the heart

b. Left Atrium smaller thin-walled chamber of the hearthas openings on its dorsal wall near interatrial septum for

pulmonary veins

c. Interatrial septumdivides the left and right atrium

d. Sinoatrial aperture oval opening on the dorsal wall of the right atrium serves as the entrance of blood from the sinus venosus

Internal Structure of the Frog’s Internal Structure of the Frog’s Heart and It’s BranchesHeart and It’s Branches

e. Ventricle large thick walled chamber

f. Muscular Pockets located at the inner wall of the ventricle

g. Atrioventricular apertures connects the atria and ventricle serves as entrance of blood to the ventricle guarded by valves which prevent back-flow of blood

h. Septa two longitudinal division within truncus arteriosusdivides truncus into three channels

Parts

1.Spiral valve

2. Right atrium

3. Left atrium

4. Ventricle

5. Truncus arteriosus

6. Pulmocutaneous arch

7. Systemic arch

8. Carotid arch

Internal Anatomy of the Internal Anatomy of the Mammalian Heart Mammalian Heart

a. ventriclesconstitute the bulk of the heart thick walled and highly muscular

b. apex posterior narrow portion

c. base broad anterior portion

d. atria anterior to the basethin-walled and dark colored

right atrium- biggerleft atrium- smaller

where pulmonary v. enters


e. Interatrial septum separates right from left atrium

f. Sinus venosus in adults is incorporated into this region as Sinoatrial node (SA)

g. Interventricular septum completely partitions the ventricles

right ventricle is smaller and thinner walled

left ventricle includes the apexbigger and thicker walled


h. right atrio-ventricular apertureopening between the right atrium and right ventricleguarded by three membranous flaps or TRICUSPID VALVES

i. left atrio-ventricular apertureopening between the left atrium and left ventricleguarded by two membranous flaps or BICUSPID VALVES or

MITRAL VALVEj. trabeculae carne

muscular ridges that deeply cleave the inner walls of the ventriclesk. papillary muscles

pointed finger-like musclesproject from the walls of the ventricles


l. chordae tendinae fine thread-like fibers connecting the free edges of the

tricuspid and bicuspid valves to the tip of the papillary muscles

m. pulmonary artery opening in the right ventricles where the blood leaves

n. semilunar valves guards the exists of the right ventricle to the aortaguards the exists of the left ventricle to the pulmonary

arteries

NERVOUS SYSTEM AND NERVOUS SYSTEM AND SENSORY ORGANSSENSORY ORGANS

Types of Nervous SystemsTypes of Nervous Systems1. Diffuse type or nerve net

Simplest type of N.S. Found in Coelenterates (Hydra)

– Termed nerve net because it consists of a network of nerve cells, each with a number of processes radiating from the cell body in all directions

– The processes of neighboring nerve cells connects to one another to form a continuous network.

– Called diffuse type because primitive nerve cells (neuries or protoneurons) non-polar; nerve impulses are conducted in all directions from point of stimulation, no definite pathways

– In higher types of nerve cells, nerve impulses travel in one direction only (cell body axon)

Main distinguishable characteristic: Lack of centralization or absence of concentrations of nerve cell bodies at certain areas of the body of the animal.

2. Ladder type Dugesia (flatworm) Has cephalization head regionParts: Cerebral ganglia primitive brain formed from aggregation of nerve cells Longitudinal nerve cords lie parallel to each other and pass posteriorly

along most of the entire length of the body Transverse nerves rung-like structures of a ladder that connect

longitudinal nerves into a linear seriesn hence the term ladder type of nervous system

Lateral nerves innervate the body wall and other structures, arises from transverse nerves

Types of Nervous SystemsTypes of Nervous Systems

3. Ganglionic type Found in Annelids and arthropods Consists of:A. Dorsal Brain (Cerebral ganglia)

located in the headB. Ventral Nerve Cord

extends from the brain posteriorly along the length of the rest of the body

Consists of a segmental series of paired, closely approximated ganglia which are connected by two longitudinal nerves strands

C. Longitudinal nerve strands forms double chain of ganglia

Arthropods N.S. is more centralized and has fewer ganglia due to migration and

fusion in the thorax and abdomen. Longitudinal nerve strands tend to fuse into a single strand.



4. Tubular typeFound in vertebratesTubular: vertebrate brain and spinal cord are hollow.Brain cavities, termed ventricles, are continued with the central canal of the spinal cord.

Types of Nervous System

Overall Organization of the Overall Organization of the Vertebrate N.S.Vertebrate N.S.

composed of:

1. central nervous system includes the brain and the spinal cord serves as a central exchange or switchboard

2. peripheral nervous system consists of nerve cells and nerve fibers which connect to the C.N.S. to all parts of the body

3. the sense organs

Peripheral Nervous SystemPeripheral Nervous Systemsubdivided into the:

Somatic N. S. innervates skeletal muscles, skin, and certain other body parts responsible for movement of various parts of the body thru reflex actions

and conscious control of will

Autonomic/Visceral N.S. innervates cardiac muscles, smooth muscles, and glands governs and controls the functions of the viscera (heart, digestive tract,

glands, etc…) carried out automatically and controlled at the unconscious level Includes the:

Sympathetic N.S.Parasympathetic N.S.

*Both have antagonistic effects

Autonomic Nervous SystemAutonomic Nervous System It consists of the cranial nerves and spinal nerves from the

spinal cord.Frog: 10 pairs Man: 12 pairs

Spinal nerves consist of:

a. Sensory/Afferent Transmit impulses from the receptors to the C.N.S.

b. Motor efferent Transmit impulses from the C.N.S. to the effectors

Spinal NervesSpinal Nerves 1st to 9th Spinal Nerve exit through the intervertebral

foramina 10th gets out through the lateral foramina at the anterior third

of the urostyle Glands of Swammerdam or Periganglionic glands: masses of

white calcareous materials found at the sites of the exit of the nerves.

Spinal NervesSpinal NervesSpinal nerves

1st – connect with larger 2nd spinal nerve to form Brachial plexus2nd – largest of the first three spinal nerves and connects with them to form

Brachial plexus- main trunk extends to the forelimb as the brachial nerve

3rd - connect with the larger 2nd Spinal Nerve to form the Brachial Plexus. *Plexus- a network of communicating nerve fibers

4th - extend postero-laterally do not form a plexus.5th - extend postero-laterally do not form a plexus.6th - extend postero-laterally do not form a plexus7th - are sharply directed posteriorly and goes along with the 8th and 9th

spinal nerve to form the lumbo-sacral or sciatic plexus.8th - Joins with the 9th to form the Sciatic Nerve9th - Joins with the 8th to form the Sciatic Nerve10th - lies close to the side of the Urostyle (hard to see)

Autonomic Nervous SystemAutonomic Nervous System consists of 2 delicate chains of ganglia (Sympathetic Trunk) and several unpaired gangliaa. Sympathetic Trunk

originate from the cranial cavity lie alongside the systemic arch and dorsal aorta

b. Jugular foramina located lateral to the occipital condyles

c. Sympathetic ganglia node like structures found at varying intervals along the trunks

d. Rami communicantes or Visceral rami connected to the sympathetic ganglia * P.N.S. does not form an orderly chain of ganglia and need not be dissected.

Central Nervous SystemCentral Nervous System The brain and the spinal cord are enveloped by two meninges

or membrane:Outer pigmented Dura Matter Pia Matter

*Both inseparately adhere to the nervous tissue. Subdural Space in between the 2; filled with cerebrospinal

fluid

Parts of the Frog BrainParts of the Frog Brain1. Telencephalon or cerebral hemispheres

Enlarged elongated bodies separated medially by a groove, found at the anterior part of the brain

Found here are complex centers of consciousness and sensations2. Olfactory bulbs3. Telencephalon

where the first pair of cranial nerves, the olfactory nerves originate.4. Olfactory nerves – first pair of cranial nerves5. Diencephalons (thalamencephalon or twixtbrain

depressed unpaired lobe posterior to the Telencephalon The relay center for sensory impulses; centers of regulating body

temperature, water balance; carbohydrate and fat metabolism6. Anterior Choroid Plexus

thin membrane that acts as the roof of dicencephalon7. Pineal body or epiphysis

arising from the median dorsal surface of the diencephalon has an endocrine function

8. Mesencephalon or optic lobes a pair of rounded bodies posterior to the diencephalons where visual and auditory reflex centers are located.

9. Metencephalon or cerebellum the narrow fold posterior to the mesencepahlon Responsible for muscle coordination and proprioception

10. Myelencephalon or medulla oblongata Triangular portion posterior to the metencephalon. Its broad anterior portion

is partly covered dorsally by the metencephalon, while its tapered portion is continuous with the spinal cord

Located in the various areas of the medulla oblongata are the reflex centers that control respiration, heart rate, dilation and constriction of blood vessels and swallowing.

11. Fourth ventricle The triangular cavity of the which is covered by a thin highly vascular

membrane12. Posterior choroids plexus

thin highly vascular membrane covering fourth ventricle

Parts of the Frog BrainParts of the Frog Brain

12. Filum terminale tapering posterior portion where the spinal cord extends from the

myelencephalon occupies the cavity of the urostyle

13. dorsal median sulcus groove that extends along the median region of the spinal cord

14. Ventral median fissure the corresponding ventral groove of the Dorsal median sulcus


Ventral Aspect15. Optic chiasma

ventral side of the dicencephalon formed by the crossing of the fibers of the second pair of cranial

nerves16. Optic nerves

the second pair of cranial nerves17. Infundibulum

bilobed extension of the diencephalons, posterior to the optic chiasma

18. Hypophysis or pituitary body a small round gland attached to the postero-ventral side of the

infundibulum, which lies on a depression on the floor of the skull The hypophysis has endocrine functions regulated by

neurosecretions produced in the diencephalons 19. Sella tursica

depression on the floor of the skull


Ventricles of the brain

1. first and second lateral ventricles cavity of the cerebral hemispheres communicate with the cavity of the olfactory bulbs

2. rhincoeles cavity of the olfactory bulbs

3. third ventricle communicates with the lateral ventricles through narrow opening

foramen of Monro4. Foramen of Monro

narrow opening of the third ventricle


Ventricles of the brain

5. optic ventricles or opticoeles expanded cavities in the mesencecephalon

6. Iter or aqueduct of Sylvus narrow cannal where the third and optic ventricles connect with

forth ventricle7. Fourth ventricle

continous posteriorly with the cavity of the spinal cord8. Central canal or canalis centralis

cavity of the spinal cord


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Sense OrgansSense OrgansThe Eyes1. Sclerotic coat

the outermost coat of the eye Tough, opaque, protective structure that maintains the shape of the

eyeball.2. Cornea

anterior portion of the sclerotic coat 3. Conjuctiva

thin, transparent membrane covering the outer surface of the cornea and continuous with the inner surface of the eyelids

4. Optic Nerve White, thread-like structure that can be observed at the posterior part of

the eyeball.5. Retractor bulbi

muscles attached to the sclerotic coat around the optic nerve which pulls the eye into the orbit

*Six other muscles are attached to the eyeball at different anges are responsible for other eye movement.

The Ear Sense organs of hearing and equilibrium Frog’s ear is composed of two parts:

Middle ear1. external tympanic membrane2. columella

rod-like bone located inside the tympanic cavity extends across the tympanic cavity to the wall of the skull.

3. Eustachian tube where tympanic cavity connects with buccal cavity

Inner ear

Sense OrgansSense Organs

Frog Ear

http://imnh.isu.edu/digitalatlas/bio/amph/smpkey/annoimg/large/raca.jpg

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DIGESTIVE SYSTEM