DIGESTIVE SYSTEM Introduction concerned with the function of

DIGESTIVE SYSTEM

Introduction • 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 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 TYPE • mouth and anus are present • may be subdivided into the digestive tract, the digestive glands, and the accessory structures

Coelom, Peritoneum, and Mesenteries Coelom • – cavity containg the visceral organs divided into: a. small pericardial cavity – contains the heart b. 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 wall b. visceral peritoneum – covers most visceral organs

Coelom, Peritoneum, and 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 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

4 1. Vomerine Teeth 3. Opening to the Eustachian Tube 2. Internal Nares 4. Maxillary Teeth

Digestive Tube 1. esophagus – short tube connecting the oral cavity to the stomach 2. Stomach – bag shaped muscle Parts of stomach: a. cardiac end – anterior portion continuous with the esophagus b. pyloric end – posterior portion continuous with the small intestine c. greater curvature – outer curvature d. lesser curvature – inner curvature e. rugae – lines of the inner wall of the stomach 3. pyloric sphincter – constriction at the junction of the stomach and the small intestine

Digestive Tube 4. 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 stomach b. 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 Tube 6. 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 SYSTEM

Types 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 RESPIRATORY SYSTEM

AQUATIC RESPIRATORY SYSTEMS Gills of Fishes -are delicate comb-like structures a. Operculum – covers the gills b. Gill chamber – part of the pharynx c. 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 specimen e. 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 SYSTEMS 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 SYSTEMS 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 System

Frog’s Excretory System Kidney ü flat, ovoid reddish organs lying in a space ü retroperitoneal ü adrenals maybe observed as the yellowish streaks on the ventral surface Cisterna Magna ü space between the muscles of the dorsal body wall and the peritoneum Mesonephric or Wollfian Duct ü thread like tubular structure on the lateral side of each kidney ü continues posteriorly beyond the kidney and enters the cloaca separately on its dorsal wall Urinary Bladder ü 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 Kidney 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 SYSTEM

Function 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 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 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 SYSTEM Blood Vascular System Composed of: a. Blood b. 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 venules Arterioles small arteries Venules small veins

Lymphatic System Composed of: – Lymph vessels – Lymph spaces – Lymph circulating fluid Where is it located? Dorso-lateral subcutaneous connective tissue Tissue connecting the skin to the body wall Dorsal subcutaneous lymph 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

HEART a. 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 pericardium d. Transverse Septum Separates the pericardial cavity and the pleuroperitoneal cavity e. Pleuroperitoneal Cavity contains the visceral organs (minus the heart)

CHAMBERS OF THE HEART Sinus 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 arteries arises 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 Aspect 1. Ventricle 2. Right Atrium 3. Left Atrium 4. Sinus Venosus 5. Pulmonary Vein 6. Pulmocutaneous Arches 7. Systemic Arches 8. Common Carotid Arches

VENOUS SYSTEM Principal 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

VEINS Left/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 cava a. External jugular vein anterior b. Innominate vein c. Subclavian vein Brachial vein Musculocutaneous vein

PORTAL VEINS Hepatic Portal System Consist of the: a. Hepatic portal vein drains blood from the following tributaries gastric vein from the stomach splenic vein from the spleen pancreatic vein from the pancreas intestinal veins from the small intestines Ventral abdominal vein brings the drained blood to the liver b. Hepatic vein

PORTAL VEINS Renal Portal System Consist 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 wall c. Oviduct (for females) d. Femoral vein anterior and dorsal sides of the thigh and the rest of the hindlimb e. 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 vein f. Sciatic vein posterior side of the thigh

Pulmonary Veins from the lungs they enter the left atrium

ARTERIAL SYSTEM Arteries ü thick-walled, light colored, generally deeply set in the body ü blood flow is pulsating or in spurts ü carry oxygenated blood (minus the pulmonary artery)

ARTERIAL SYSTEM Ventral 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 arteriosus 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 Artery Subclavian 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 artery anterior mesenteric artery

Branches of Systemic Artery Posterior 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 Heart and It’s Branches a. Right Atrium larger thin walled chamber of the heart b. Left Atrium smaller thin-walled chamber of the heart has openings on its dorsal wall near interatrial septum for pulmonary veins c. Interatrial septum divides 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 Heart 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 arteriosus divides 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 Mammalian Heart a. ventricles constitute 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 base thin-walled and dark colored right atrium- bigger left atrium- smaller where pulmonary v. enters

Internal Anatomy of the Mammalian Heart 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 apex bigger and thicker walled

Internal Anatomy of the Mammalian Heart h. right atrio-ventricular aperture opening between the right atrium and right ventricle guarded by three membranous flaps or TRICUSPID VALVES i. left atrio-ventricular aperture opening between the left atrium and left ventricle guarded by two membranous flaps or BICUSPID VALVES or MITRAL VALVE j. trabeculae carne muscular ridges that deeply cleave the inner walls of the ventricles k. papillary muscles pointed finger-like muscles project from the walls of the ventricles

Internal Anatomy of the Mammalian Heart 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 aorta guards the exists of the left ventricle to the pulmonary arteries

NERVOUS SYSTEM AND SENSORY ORGANS

Types of Nervous Systems 1. 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.

Types of Nervous Systems 2. Ladder type Dugesia (flatworm) Has cephalization head region Parts: 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 Systems 3. Ganglionic type Found in Annelids and arthropods Consists of: A. Dorsal Brain (Cerebral ganglia) B. located in the head 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.

Types of Nervous Systems 4. Tubular type Found in vertebrates Tubular: 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 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 System subdivided 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 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 Nerves 1 st to 9 th Spinal Nerve exit through the intervertebral foramina 10 th 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 Nerves Spinal nerves 1 st – connect with larger 2 nd spinal nerve to form Brachial plexus 2 nd – 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 3 rd - connect with the larger 2 nd Spinal Nerve to form the Brachial Plexus. *Plexus- a network of communicating nerve fibers 4 th - extend postero-laterally do not form a plexus. 5 th - extend postero-laterally do not form a plexus. 6 th - extend postero-laterally do not form a plexus 7 th - are sharply directed posteriorly and goes along with the 8 th and 9 th spinal nerve to form the lumbo-sacral or sciatic plexus. 8 th - Joins with the 9 th to form the Sciatic Nerve 9 th - Joins with the 8 th to form the Sciatic Nerve 10 th - lies close to the side of the Urostyle (hard to see)

Autonomic Nervous System consists of 2 delicate chains of ganglia (Sympathetic Trunk) and several unpaired ganglia a. 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 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 Brain 1. 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 sensations 2. Olfactory bulbs 3. Telencephalon where the first pair of cranial nerves, the olfactory nerves originate. 4. Olfactory nerves – first pair of cranial nerves 5. 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 metabolism 6. Anterior Choroid Plexus thin membrane that acts as the roof of dicencephalon 7. Pineal body or epiphysis arising from the median dorsal surface of the diencephalon has an endocrine function

Parts of the Frog Brain 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 membrane 12. Posterior choroids plexus thin highly vascular membrane covering fourth ventricle

Parts 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

Parts of the Frog Brain Ventral Aspect 15. Optic chiasma ventral side of the dicencephalon formed by the crossing of the fibers of the second pair of cranial nerves 16. Optic nerves the second pair of cranial nerves 17. 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

Parts of the Frog Brain 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 Monro 4. Foramen of Monro narrow opening of the third ventricle

Parts of the Frog Brain Ventricles of the brain 5. optic ventricles or opticoeles expanded cavities in the mesencecephalon 6. Iter or aqueduct of Sylvus narrow cannal where third and optic ventricles connect with forth ventricle 7. Fourth ventricle continous posteriorly with the cavity of the spinal cord 8. Central canal or canalis centralis cavity of the spinal cord

F R O G B R A I N

Sense Organs The Eyes 1. 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.

Sense Organs The Ear Sense organs of hearing and equilibrium Frog’s ear is composed of two parts: Middle ear 1. external tympanic membrane 2. 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

Frog Ear