Histology of the Liver and Pancreas PDF

HISTOLOGY OF THE LIVER DIGESTIVE SYSTEM Description: Largest structure of the body cavity Concerned with o Brown in color o ingestion of food...

HISTOLOGY OF THE LIVER DIGESTIVE SYSTEM Description: Largest structure of the body cavity Concerned with o Brown in color o ingestion of food o Secretes digestive juice (bile) o physical and chemical digestion of food ➔ Bile - is green/yellow in color and is a fluid or o absorption of nutrients digestive enzyme that aids in the digestion of o elimination of undigested remains. fats in food Includes ◆ Stored in the gallbladder o Digestive tract or alimentary canal ◆ Bile travels in the gallbladder o Digestive glands through the bile duct ➔ Bile duct - passes through the pancreas towards the intestine Has three lobes: o Right lobe o Left anterior lobe o Left posterior lobe Hepatic lobules o Separated from each other by connective tissue partition or septa. o Large central vein - found at the center of the lobule ➔ Radiating from the central vein are polygonal-shaped hepatic cells or hepatocytes arranged into cords or plates. o Hepatic sinusoids - spaces found in between hepatic plates ➔ Lead toward the periphery of the hepatic lobule. Hepatocytes o Liver cells Liver receives blood from two different sources: o Portal canals/vein - found around each lobule within DIGESTIVE SYSTEM OF THE TOAD the septa. The toad has a complete digestive tract, with two ➔ contains branches of the portal veins, openings: hepatic arteries, and bile ducts. o Mouth ➔ Major source of the blood of the liver o Cloaca ➔ Carries veinous blood from the intestine, pancreas, and spleen The main parts of the tract: o Hepatic artery - brings oxygenated blood to the liver o Mouth Portal triad: o Oral or buccal cavity o Portal vein o Pharynx o Hepatic artery o Esophagus o Bile duct o Stomach o Small intestine o Large intestine o Rectum o Cloaca The digestive glands include: o Liver, o Gallbladder o Pancreas o Note: These glands are not found within the tract, but they secrete digestive juices that enter the alimentary canal through ducts. The bile duct is different from the vein and artery in that it is lined with simple columnar epithelium. DO | BLOCK05191D 1  panindigan mo ‘yan beh pinili mo ‘yan Pancreas makes trypsin, insulin, and glucagon o Trypsin - breaks down protein o Insulin - tells cells to store glucose from the bloodstream as glycogen o Glucagon - tells cells to release stored glucose to the bloodstream (raises glucose level in the blood) HISTOLOGY OF THE PANCREAS Description: Located in the inside curve of the stomach o Gland that often falls apart during preservation process o Has both the endocrine and exocrine functions. Exocrine pancreas o perform the digestive function Intralobular duct o consist of closely packed acini arranged into small o Made of simple cuboidal epithelium lobules o Seen within the lobules Pancreatic acini o Receive secretions from intercalated discs o consists of pyramidal-shaped cells surrounding a Different types of Islets of Langerhans lumen. o Alpha cells - produces glucagon Isolated pancreatic islets/Islets of Langerhans o Beta cells - produces insulin o Produces hormones and is secreted to the bloodstream o Help control the level of glucose in the blood o Found within the masses of acini cells o Are pale-staining structures composed of cells arranged in cords. o Have rich capillary network. o Perform the endocrine function of the pancreas. Head of the pancreas o Widest part of the pancreas o Found on the right side of the abdomen o Nestled on the curve of the duodenum ➔ Duodenum - first part of the small intestine Body of the pancreas o Middle of the pancreas Tail of the pancreas o Tip of the pancreas o Located on the left side of the abdomen and in DIGESTIVE SYSTEM OF THE FROG close proximity to the spleen BUCCAL CAVITY OF THE FROG DO | BLOCK05191D 2  panindigan mo ‘yan beh pinili mo ‘yan 2. Place the frog in the dissection tray on its back. Frog is in a ventral position. Should have candle wax where the frog can be pinned. 3. The cloaca, which is where you will begin the incision to open the frog’s body cavity, should be between the frog’s hind legs. Use scissors to lift the skin. 4. Cutting open the torso with an “I” pattern. Upper and lower lip folds o The skin folds in the margin of upper jaw and lower jaw Median subrostral fossa 5. Lift the flaps of the body wall and pin back. o A prominent depression at the tip of the upper jaw Tuberculum prelinguale o A median elevation at the tip of the lower jaw Sulcus marginalis o A pair of deep grooves found at the inner margin of the upper jaw. o receives the elevation at the lower jaw Maxillary teeth o row of small teeth located along the margin at the upper jaw 6. There is a spiderweb-like membrane that covers Vomerine teeth many of the organs, which you may have to o Another set of teeth is found on the roof of the carefully pick off to get a clear view of the organs mouth inside. Internal nares o anterolateral openings Eyeball prominences o Bulging regions at the posterior half of the roof of the mouth Openings of the Eustachian tube o Found on the posterolateral side of the eyeballs medial to the angles of the jaw is a pair of openings Tongue o Is attached to the floor of the mouth cavity near the CAVITIES OF THE FROG anterior end by a short pedicle. Vocal sacs o Two slit-like openings in the posterolateral corner of 1. Pericardial Cavity the floor of the tongue. Anterior o Often lacking in females Small Esophagus Contains the heart o Behind the mouth is the pharynx that leads into this opening of a short distensible tube (esophagus) Glottis 2. Pleuroperitoneal Cavity o Laryngeal prominence with a vertical slit-like Posterior opening ventral to the esophagus Large Houses the lungs and other internal organs FROG DISSECTION or viscera Transverse septum 1. Prepare the dissection tray and get your frog. o Separates the two cavities Usually, the frog to be used is already dead Parietal peritoneum and preserved. o A glistening membrane that lines the body wall In the case of a live frog, you have to o The extension of the parietal peritoneum forms the anesthetize first by putting chloroform in the jar of the frog or pith the spinal cord of the covering layer of the intestine and other viscera. frog to numb the frog. Visceral peritoneum or Serosa o Extends to the visceral organs Mesentries DO | BLOCK05191D 3  panindigan mo ‘yan beh pinili mo ‘yan oSuspends the digestive tract 7. Mesogaster o are extensions also of the parietal peritoneum. portion of the dorsal mesentery supporting Dorsal mesentery the stomach o the part that attaches the digestive tract for most of its length to the median dorsal line 8. Small intestine Ventral mesentery Absorption of digested nutrients occurs here o attaches the organs to the midventral line Duodenum - straight portion o is usually lost except in the region of the liver and Ileum - curved portion ○ Held together by a membrane the urinary bladder. (mesentery) ○ Blood vessels running through the DIGESTIVE SYSTEM OF THE FROG mesentery carry and absorb nutrients away from the intestine Part of the dorsal mesentery supporting the small intestine and the large intestine is the mesentery proper and the mesorectum, respectively. 9. Large intestine Wider intestine Leads to the cloaca ○ Cloaca - last stop before solid waste, sperm, eggs, and urine exit the frog’s body ➔ chamber that serves as a common passageway to the outside for both digestive and urogenital systems ➔ It terminates at the cloacal aperture. 10. Anus ORGANS OF THE PLEUROPERITONEAL CAVITY Opening outside the body 1. Liver large, trilobed, brownish organ occupying the anterior half of the pleuroperitoneal cavity. 2. Gallbladder stores the bile secreted by the liver. 3. Hepatic ducts from the liver and cystic ducts from the gallbladder may be traced to the point where it joins the common bile duct. 4. Common bile duct enters the duodenum of the small intestine. 5. Esophagus Leads from the frog’s mouth to the stomach 6. Stomach Curving underneath the liver First major site of chemical digestion Can be seen dorsal to the liver Cardiac region - area nearest the esophagus ○ is guarded internally by a cardiac sphincter, a ring of smooth muscle. Fundus - bulges anteriorly Pylorus - the narrow end when the stomach is followed posteriorly ○ guarded internally by the pyloric sphincter DO | BLOCK05191D 4  panindigan mo ‘yan beh pinili mo ‘yan 14. Oviduct Curly structure outside the kidney Where eggs are produced Also found in males as a vestigial oviduct (looks similar but has no purpose) 11. Kidney Flat bean-shaped organ located at the lower back of the frog near the spine Often dark-colored but a little reddish/brown Filters waste from the blood Fatty bodies - stored fat of the frog 12. Testes Located on top of the kidney Pale-colored and roundish 13. Spleen Dark red Spherical or round and dense Serves as a holding area of the blood 15. Rugae longitudinal folds in the inner wall of the stomach 16. Pyloric sphincter similar to the cardiac sphincter consists of a circular muscle that regulates the flow of food into the small intestine. DO | BLOCK05191D 5  panindigan mo ‘yan beh pinili mo ‘yan Two stages of respiration: RESPIRATORY SYSTEM o External respiration - the exchange of gases Description: for obtaining oxygen and getting rid of between the environment and the respiratory carbon dioxide. organs o Eliminates the body from a surplus of CO2 o Internal respiration -the exchange of gases Respiration between body fluids and tissue cells. o The exchange of gases Respiration in an adult frog occurs in 3 different ways: HISTOLOGY OF THE LUNGS 1. Cutaneous respiration Respiratory system Takes place through the moist surface of the o Is comprised of organs that help in the intake and outer skin supply of oxygen to tissues as well as to get rid of Takes place all the time regardless if the frog carbon dioxide. is in or out of the water. Allows respiratory gases to readily diffuse directly down their gradients between their blood vessels and the surroundings. When the frog is in the water, the frog breathes through its skin. When the frog is outside of the water, the moist skin of the frog helps absorb dissolved oxygen from the air. 2. Buccal respiration Takes place through the lining of bucco-pharyngeal cavity Mouth is permanently close, nostrils are open. Floor of buccal cavity is alternately raised and lowered, which allows air to be drawn in and out of the buccal cavity, Mucous epithelial lining of the buccal cavity is rich with blood vessels (capillaries) which Bronchus absorb O2 and give off CO2 o Small tube that leads to the lungs 3. Pulmonary respiration Alveoli Takes place through the lungs o Lined with a thin epithelium which is richly supplied with blood capillaries (contain deoxygenated blood Frogs and toads utilize various respiratory organs, such as for gas exchange) the lungs, skin, and mucous lining of the mouth. o Oxygen in the inhaled air diffuse blood while carbon o These organs are characterized by a dioxide is released to alveoli semi-permeable membrane through which gases o numerous chambers of the lungs that sometimes diffuse readily. interconnect with one another. o Interalveolar septum - very thin partition between alveoli Oxygen Arteriole o is obtained from the environment o Small artery that leads to the capillaries because it is needed for metabolism. Carbon dioxide o produced as a by-product of metabolism o Is released into the environment Inspiration o Inhalation or taking in oxygen Expiration o Exhalation or giving off CO2 Frogs and toads utilize various respiratory organs, such as the lungs, skin, and mucous lining of the mouth. o These organs are characterized by a semi-permeable membrane through which gases diffuse readily. DO | BLOCK05191D 6  panindigan mo ‘yan beh pinili mo ‘yan o Egg-shaped in a living toad. Alveoli o Singular: alveolus o Membranous sacs lined by small air pockets o Where gas exchange takes place RESPIRATORY SYSTEM: ANATOMY CIRCULATORY SYSTEM Primary functions: o Transport of respiratory gases, food materials, waste products, hormones and minerals within the body o Defense against foreign organisms o Maintenance of body temperature in warm-blooded or homeothermic animals. Vertebrates (Toads) have a closed type of circulatory system composed of: 1. Heart Nostrils pumps deoxygenated blood to the lungs and o pair of openings at the anterolateral part of the distribute oxygenated blood to all the organs. snout. 2. Arteries and Arterioles o Also called external nares Vessels o Lead to the internal nares convey oxygenated blood from the heart to Openings of the Eustachian tube the smallest vessels o Found at the roof of the oral cavity, near the angle Pulmonary artery - delivers deoxygenated of the jaw blood to the lungs for oxygenation o The tube connects the mouth cavity with the cavities of the middle ear. 3. Capillaries Glottis Smallet vessels o slit-like opening at the posterior region of the Found in various tissues and organs of the pharynx body with the exception of the pulmonary o opens downward into the cavity of the larynx artery Larynx o Voice box 4. Venules and Veins o supported or stiffened by cartilages Deoxygenated blood is collected from the ➔ Arytenoid cartilages - anterior pair capillaries to the venules and to the veins ➔ Cricoid cartilages - posterior pair before it returns to the heart. Vocal cords Pulmonary vein - collects oxygenated blood o thin elastic bands in each half of the larynx. from the lungs and delivers it back to the Bronchus heart for distribution throughout the body. o Is connected to the larynx o Lead to the lungs o Extremely short tube Lungs o collapsed in the preserved toad DO | BLOCK05191D 7  panindigan mo ‘yan beh pinili mo ‘yan Atrioventricular valves o thin flaps between the atria and ventricle Open circulatory system - o may not be seen in the specimen blood is not enclosed in blood vessels Semilunar valves Closed circulatory system - o flaps that open into conus arteriosus blood is enclosed in blood o may not be seen in the specimen vessels ANATOMY OF THE FROG’S HEART FROG’S HEART Heart o Cone-shaped muscular organ lying in the thorax. o Muscular central pumping station o Drives blood to the circulatory system o Lies mid-ventrally inside the arterial trunk region o Has a broad base that is directed anteriorly and a narrow apex posteriorly Three chambers of the heart of a frog: o 2 Atria or Auricles ➔ Left Auricle ➔ Right Auricle ➔ Are dark in color and lies anteriorly o 1 Ventricle ➔ Pink colored ➔ Triangular or conical and lies posteriorly Sinus Venosus o A dark colored, thin-walled, and triangular chamber ASSOCIATED STRUCTURE AND PARTS o Attached dorsally to the heart OF THE HEART Truncus Arteriosus o Tubular chamber that arises anteriorly from the Pericardium right ventral side of the ventricle o a thin transparent two-layered membrane covering the heart o Sac-like structure that contains lubricating pericardial fluid o Parietal pericardium - outer wall of the pericardium o Visceral pericardium - inner wall of the pericardium o Pericardial fluid - lubricating fluid Pericardial cavity o coelom/cavity where the heart is situated Atria o Singular: atrium o two globular structures atop the ventricle Ventricle o most posterior conical structure of the heart Conus arteriosus o one-shaped tube arising from the ventricle on its ventral side Sinus venosus When the frog is sectioned, the internal structure is visible. o this is best seen when the tip of the ventricle is o Internal structure is hollow and muscular lifted In order to keep the unidirectional flow of the blood, the o a thin-walled triangular sac on the dorsal side of various chambers are separated by the vault. the heart and is continuous with the right atrium. INTERNAL STRUCTURE OF THE HEART Interatrial septum o wall separating the right from the left atrium DO | BLOCK05191D 8  panindigan mo ‘yan beh pinili mo ‘yan COMMON CAROTID ARTERY Description: short vessel that runs forward and outward Divides into two: 1. External carotid artery or Lingual artery Smaller and inner branch supplies blood to the thyroid gland, muscles of the hyoid apparatus, and the tongue, and the internal carotid artery 2. Internal carotid artery The bigger and outer branch Divides further into three: ○ Palatine artery - supplying blood to the roof of the oral cavity. ○ Cerebral artery - supplies blood to the brain ○ Ophthalmic artery - supplies blood to the eyes FROG’S ARTERIAL SYSTEM Arteries (except the pulmonary arteries) o supply oxygenated blood to different parts of the body. Conus arteriosus o Located on the ventral side of the heart between the auricles/atria o cone-shaped or bulb-shaped structure o Anteriorly, it divides into left and right branches (truncus arteriosus) Truncus arteriosus o Divides into three branches ➔ Common Carotid artery ➔ Systemic Arch Carotid gland ➔ Pulmocutaneous artery o Found at the base of the internal carotid artery o Oval structure o Regulates the blood flow going to the head SYSTEMIC ARCH Other name: Aortic Arch Description: the middle branch of the truncus arteriosus. o Longest of the three arches o Has the greatest distribution of blood Dissection: Can be seen by tearing the parietal peritoneum and gently deflecting the lungs and other internal organs on one side. Four smaller branches arise from the systemic arch: o Laryngeal artery - supplies blood to the larynx and jaw DO | BLOCK05191D 9  panindigan mo ‘yan beh pinili mo ‘yan o Esophageal artery - supplies blood to the o Behind the dorsal aorta esophagus o Supplies blood to the dorsal wall ➔ May arise from the occipital vertebra Oviducal arteries o Occipital artery or Occipito-vertebral artery - o Found on the ventral side of the dorsal aorta at the supplies blood to the orbit and nose region of the cloaca o Posterior vertebral artery - supplies blood to the o A branch that goes to the oviduct in female frogs vertebral column Subclavian artery o Extends laterally and becomes the branchial artery that supplies blood to the forelimbs Following the dorsal aorta posteriorly, it eventually divides into left and right common iliac arteries. DORSAL AORTA Follow one of the iliac arteries and look for the Description: formed when the left and right systemic epigastricovesical artery, which further divides into: arches join together. o Epigastric artery - located anteriorly; supplies blood Dissection: can be seen best by tearing the remaining to the abdominal wall portions of the parietal peritoneum. o Rectovesical artery - located posteriorly; supplies Coeliacomesenteric artery blood to the cloaca and urinary bladder o Found slightly below the point of junction of the Femoral artery systemic arches o Found at the region of the thigh o Single-layer artery o Supplies blood to the muscles and anterior part of o Divides into two: the thing ➔ Coeliac artery Common iliac continues to the entire length of the hindlimb ◆ Left gastric artery - supplies blood as the sciatic artery. to the left side of the stomach and left side of the pancreas ◆ Hepatic artery - supplying blood to the liver and portions of the pancreas ◆ Pancreatic arteries - go to the rest of the pancreas ➔ Anterior mesentric artery ◆ Splenic artery - supplying blood to the spleen ◆ Intestinal arteries - supplying blood to the small intestine ◆ Anterior hemorrhoidal artery - supplying blood to the large intestine and cloaca Renal artery o Branches going to the kidneys o Dorsal aorta sends off 5-6 pairs of small renal arteries in a series into both the kidneys Spermatic arteries o Supplies blood to the testes for males Ovarian arteries o Supplies blood to the ovaries of the female Posterior mesenteric artery o Arises from the posterior end of the dorsal aorta and sometimes from the anterior mesenteric o Goes to the large intestine or rectum Adiposal arteries o Supplies blood to the adipose tissues Lumbar arteries DO | BLOCK05191D 10  panindigan mo ‘yan beh pinili mo ‘yan ANTERIOR VENA CAVA Right and left precavals collect venous blood from the PULMOCUTANEOUS ARTERY anterior part of the body. Description: posterior branch of the truncus arteriosus Each precaval is formed by the union of three major veins that eventually divides into the pulmonary artery and which meet simultaneously: cutaneous artery. o External jugular vein - formed by the slender and o Pulmonary artery - carries blood to the lungs sinus lingual from the tongue and mandibular from the outer margin of the jaw. o Cutaneous artery - goes anteriorly and dorsally o Subclavian vein - formed by the brachial from the behind the tympanum and divides into: forelimb and musculocutaneous from the side of the ➔ Auricularis artery - supplies blood to the body and head. lower jaw o Innominate vein - formed by the internal jugular ➔ Dorsalis artery - supplies blood to the dorsal from the cranial cavity and orbit and subscapular part of the skin from the shoulder and back of the arm. ➔ Lateralis artery - supplies blood to the lateral part of the skin POSTERIOR VENA CAVA FROG’S VENOUS SYSTEM Differentiated into: o Systemic veins o Portal Veins o Pulmonary veins Deoxygenated blood from the rest of the body travels towards the heart in three large vessels that all open to the sinus venosus: o 2 Anterior Vena Cava o 1 Posterior Vena Cava Description: a large dark-colored vein o Lies ventral to the dorsal aorta Divides into three: o Renal veins ➔ Posterior end is formed between two kidneys from which it drains blood by 5-6 pairs of renal veins o Spermatic or Ovarian veins ➔ Genital veins ➔ Received from gonads directly or through the interior part of renal vein o Hepatic veins ➔ Short pair ➔ Opens to the posterior angle of the sinus venosus RENAL PORTAL SYSTEM Frogs have well-developed portal systems Description: veins which carry blood to a capillary system in the kidney DO | BLOCK05191D 11  panindigan mo ‘yan beh pinili mo ‘yan Blood of each hind leg is connected by two veins: o Outer Femoral vein ➔ On entering the abdominal cavity, the femoral veins divide into: ◆ Dorsorenal portal ◆ Ventral pelvic vein - while running along the outer border of kidney, on its side, it receives blood from the lumbar region via a dorsal lumbar vein o Inner sciatic vein Renal portal vein - enters the kidney by various branches which break up into capillaries Pelvic veins of both sides are united to form the anterior abdominal vein o Receives blood from urinal bladder and ventral abdominal wall UROGENITAL SYSTEM Description: primarily involved in assisting the frog in carrying out urine excretion and reproduction. Urogenital o is a combination of the Greek word “ouro” meaning urine and “genitales" refers to reproduction. Functionally, these are two separate systems, namely the urinary or excretory system and reproductive system. o Develop from a common germ layer origin and utilize common ducts to release their products. Hence, they are usually considered together. o Are situated closely in frogs Excretory system consists of: o Kidneys o Urinary Bladder o Urete o Cloaca Organs of the male reproductive system: o Testes o Sperm ducts o Cloaca Organs of the female reproductive system: o Ovaries o Oviducts o Uterus o Cloaca KIDNEYS Description: main organ of the excretory system Position: These lie dorsal to all other organs in the abdominal cavity and to the peritoneum, thus retroperitoneal in position. Composition: made up of nephrons o Nephrons - remove waste products of metabolism from the body as well as regulate the amount of ions inside the body of the animal. Mesonephric ducts/Wolffian ducts o Collects urine from the kidneys o Convey urine to the urinary bladder Urinary bladder o Lies ventral to the cloaca o Sac that stores urine until it passes out of the body to the cloaca Ureter o Connected to each kidney DO | BLOCK05191D 12  panindigan mo ‘yan beh pinili mo ‘yan o Tube through which urine passes in the urinary bladder PAIRED GONADS (TESTES AND OVARY) Description: principal organs of the reproductive system of sexually reproducing animals o sites for the production of gametes. o sources of important hormones needed for the development and sexual maturation of the animal. Testes o Produce sperm Sperm o Male sex cells which move through the sperm ducts o conveyed to the outside through the kidneys and then into the mesonephric duct. Sperm ducts o Tubes that carry the sperm into the cloaca Cloaca o Exit-point of the body Ovaries o Produces eggs Eggs o Female sex cells that move through the oviducts, then uterus, then cloaca o pass through the oviduct which empties into the cloaca. HISTOLOGY OF FROG’S KIDNEY Renal corpuscles/Malpighian body o Each renal corpuscle is made up of the glomerulus (glomeruli, pl.) and the Bowman’s capsule o Glomerus - the tufts of capillaries Renal Tubule o Bowman’s capsule - is represented by the clear o Starts as a thin, double-walled ciliated cap spherical area surrounding the glomerulus. (bowman’s capsule) enclosing a bunch of Renal tubules capillaries (glomerulus) o Interspersed among the renal corpuscles o Gets blood supply from the capillaries of the o are represented by rounded structures lined with efferent arteriole and renal portal vein epithelial cells. Glomerulus Nephron o receives blood from an afferent arteriole of the renal o Made of renal corpuscles and renal tubules artery o Functional unit of a kidney. o From glomerulus, blood is collected by the efferent o It is in this structure where the process of urine arterioles, which is joined by the renal vein. formation occurs. HISTOLOGY OF FROG’S TESTES Seminiferous tubules o several compartmentalized ovoid structures represented in portions o Held together by connective tissue ➔ Where the blood capillaries, lymph vessels, nerves, muscles, and roofs of interstitial cells in between the lobule Interstitial cells o Secrete testosterone responsible for the secondary sex characteristics of the individual Germinal epithelia o Cells lining the seminiferous tubules o Function for the production of sperm cells through spermatogenesis. Immature vs mature sperm cells o Immature sperm cells - appear ovoid in shape with well-defined nucleus DO | BLOCK05191D 13  panindigan mo ‘yan beh pinili mo ‘yan ➔ Sizes vary depending on the degree of 2. Primary spermatocyte maturity. Round and larger than spermatogonia o Mature sperm cells - appear thread-like. Large round nuclei ➔ Found in bundles in the lumen of the tubules floating in spermatic fluid 3. Secondary spermatocyte ➔ When mature, sperm drop into the lumen to Arise after first meiotic division pass into the ureter through the vasa Nuclear diameter is smaller efferentia and bidder’s canal. ➔ From the ureter, they pass into the vesicular 4. Spermatids seminalis where sperm are stored. Arise Arise after meiotic division II Smaller in size Early spermatid - small and round Late spermatid - small and elongated 5. Spermatozoa Exhibit highly elongated head and tail Head - contain ellipsoid nucleus ○ Has completely condensed chromatin ○ Heads of several spermatozoa appear to be arranged in a rail that are embedded in the apical cytoplasm of sertoli cells Tail - point toward the seminiferous lumen Sertoli cells - somatic cells of the testis and are essential for testis formation and spermatogenesis ○ Facilitate the progression of germ SPERMATOGENESIS cells to spermatozoa via direct contact and by controlling the Primordial cells → spermatogonium → primary environment within the seminiferous spermatocyte → secondary spermatocyte → spermatids tubules → sperm Takes place within follicular structures called the spermatocytes that rest upon the basement membrane of HISTOLOGY OF FROG’S OVARIES the seminiferous tubules Within the ovary, the eggs are arranged into individual follicles composed of oocytes and follicle cells. The wall of ovary is composed of a visceral peritoneum which forms the germinal epithelium. 1. Spermatogonia o Internal to it is a fibrous connective tissue having First stage blood vessels, muscle fibers, and nerves constitute a large portion of the sperm cell o Gives off several small groups of cells or oogonia population in the tubule of immature frogs which form the ovarian follicle Large and round Ovarian follicle Oval nuclei o Surrounded by theca or sheet o Composed of two concentric layers of stromal cells (theca externa and theca interna) DO | BLOCK05191D 14  panindigan mo ‘yan beh pinili mo ‘yan Theca externa o Covering that surrounds the entire ovary OOGENESIS Degree of maturation of egg cells Description: process by which female germ cells undergo o can be determined by the amount of the yolky meiosis and differentiation into a mature oocyte material accumulated in the cytoplasm. Differs from spermatogenesis by: o Mature oocytes will have more accumulated yolk o Gametes formed in spermatogenesis house a and pigments. motile nucleus while nuclei from through oogenesis Germinal vesicle contain materials to initiate and maintain o Nucleus of the oocyte metabolism and development. o Its nuclear membrane is serrated. o Sperm differentiates for motility, while the egg Nucleoli develops for relatively complex cytoplasm. o Found within the nucleus o function in organizing the distribution of accumulating yolk in the growing oocyte. Follicle cells o ovoid cells lying immediately outside the cell membrane. o function in nourishing the growing oocyte. Theca interna (cyst wall) o Thin layer of connective tissue surrounding follicle cells o does not cover the whole egg cell. o It is absent at the region of future rupture during ovulation release of eggs. o The cyst wall forces the egg to separate out from the surrounding follicle cells. 1. Oogonia Arise from germ cells 2. Primary (immature) oocyte Proliferates before entering meiosis Oocyte are arrested in meiotic phase during the whole process of folliculogenesis until the gonadotropin induce signals trigger them to resume meiosis prior to ovulation 3. Follicular oocyte When immature oocyte progresses beyond the early duplicate of meiotic prophase its surrounded by follicle cells During folliculogenesis, oocyte increases in size due to the incorporation of the yolk and only Only a portion of the developing oocyte reach final maturity ○ Remaining ones (those who did not reach maturity) undergo atresia Zona pellucida o Support communication between oocyte and follicle cells o Protects oocytes, eggs, embryos during development o Regulates interactions between ovulated egg and free-swimming sperm during and after fertilization DO | BLOCK05191D 15  panindigan mo ‘yan beh pinili mo ‘yan FROG’S UROGENITAL ANATOMY MALE FROG FEMALE FROG DO | BLOCK05191D 16  panindigan mo ‘yan beh pinili mo ‘yan NERVOUS SYSTEM HISTOLOGY OF THE SPINAL CORD Description: organ system that integrates all body Description: connects the brain and PNS functions White matter o Provides a system of communication for the cells of o Composed of nerve fibers carrying ascending and the body so they can work as a team to maintain descending information homeostasis o Makes up the outer region of the spinal cord o System of communication provided by the nervous o an outer, lightly stained area system is through high-speed nerve impulses Grey matter o Receives, stores, and transmits nerve impulses that o Contains cell bodies control and coordinate the activities of the body o Located in the center of the spinal cord Integration o An inner darkly stained, butterfly-shaped or o done through transmission and processing of H-shaped structure information from the external environment or within o Has a dorsolateral extension (dorsal horn or dorsal the organism's body. cornua) and ventrolateral extension (ventral horn or Nerve impulses ventral cornua). o How information is being transmitted within this o Within the ventral horn, are cell bodies of motor system neurons, which are darkly stained, star-shaped Nerves/Tracts cells. o pathways where these impulses are conducted are Central canal through groups of neuronal axons bundled together o Center of the spinal cord o Called “nerves” when situated in the PNS o Contrains cerebrospinal fluid o Called “tracts” when situated in the CNS Dorsal root Ganglia/Nuclei o Contains afferent sensory fibers that transmit o cell bodies where these axons extend from usually signals from the periphery to the dorsal root cluster together to form ganglion o Called “ganglia” when situated outside the CNS Ventral root o Called “nuclei” when situated inside the CNS o Contains efferent motor axons Spinal nerve o Made of dorsal and ventral roots MAJOR DIVISIONS OF THE VERTEBRATE Pia mater NERVOUS SYSTEM o the membrane inseparably fused with the main mass of the spinal cord. 1. Central Nervous System Dura mater serves as the main processing center of o a loose membrane covering the spinal cord. information Meninges of the CNS includes the brain and the spinal cord. o Made of the pia mater and dura mater Dorsal fissure 2. Peripheral Nervous System o A shallow fissure that marks the median dorsal side include all other nervous tissues outside the of the cord CNS. Ventral fissure is subdivided into afferent or sensory and o Found deeper efferent or motor divisions. o mark the ventral aspect of the cord. ○ Afferent division - sends information to the CNS ○ Efferent division - carries information away from the CNS. ➔ either supplies the skeletal muscles (somatic nervous system), or the visceral organs (autonomic nervous system). DO | BLOCK05191D 17  panindigan mo ‘yan beh pinili mo ‘yan CENTRAL NERVOUS SYSTEM Description: involved receiving, analyzing, coordinating, and storing information from the different parts of the body FOREBRAIN o Sites of information processing Description: largest part of the brain Brain of the frog o is represented by the cerebrum and diencephalon. o Elongated, bilaterally symmetrical Consists of a pair of anteriorly directed olfactory lobes, a o White-colored pair of cerebral hemispheres, and a diencephalon o Situated in the cranial cavity of the skull Olfactory lobes o Surrounded by thin, pigmented, vascular tissue o Anterior small spherical structures which are fused membrane (pia mater) together in the median plane o Outside the pia membrane is the tough fibrous o Each lobe gives off an olfactory nerve membrane lining the interior of the cranial cavity o For sense of smell (dura mater) Telencephalon Meninges o Long oval structures that is separated from the o Grayish membrane that covers most part of the olfactory lobes brain and spinal cord o Coordinates the activities of the neuromuscular o Tough dura mater - adheres to the walls of the mechanisms of the body cranium and neural canal o Seat of intelligence and control in higher animals o Inner pia matter - that closely adheres to the brain Diencephalon and spinal cord o Short and paired structure of the forebrain situated Subdural space behind the cerebral hemispheres o Spach between the pia mater and dura mater o Region of the brain that controls the metabolism of o Filled with a shock-absorbing, watery, clear, fats and carbohydrates lymphatic cerebrospinal fluid (CSF) o Regulates genital functions Cerebrospinal fluid (CSF) o Posterior to the cerebrum o Found in the cavities of the brain and central canal o A depressed region of the spinal cord o Functions in processing sensory information. Cerebrum o Sometimes referred to as twist brain o the most anterior lobes of the brain Pineal body o frog’s thinking center o Club-shaped endocrine gland o constricts anteriorly to form the olfactory bulb o Arises behind the diancephalon Olfactory bulb o Hollow and thin walled stalk o extends further anteriorly to form the olfactory o Projecting from the roof of the diencephalon nerves Choroid plexus Olfactory nerves o Anterior to the pineal gland o the first pair of the cranial nerves. o Covers a portion of the diencephalon Divided into three main parts: o a network of fine blood vessels o Forebrain - prosencephalon Optic chiasma o Midbrain - mesencephalon o Crossing of the optic nerves which go to the eye o Hindbrain - rhombencephalon Infundibulum o Behind optic chiasma o Extends posteriorly and is divided by a median longitudinal group Pituitary body o Slightly covered by the infundibulum Hypothalamus o An important center regulating the whole endocrine system and other parts of the brain DO | BLOCK05191D 18  panindigan mo ‘yan beh pinili mo ‘yan ➔ X (vagus) ➔ Note: sabi ni miss sa discussion, seven but acc naman sa discussion sheet, six nerves CRANIAL NERVES MIDBRAIN Description: well-developed part of the brain o Consists of two dorsolateral round optic lobes Mesencephalon (optic lobes) o Center for impulses coming from the eyes o Represents the midbrain Description: In an adult frog, there are 10 pairs of cranial o Optic lobes and optic thalami are concerned with nerves. the control of the movements of the eye muscles o Emerge from the brain through the cranium to o Immediately posterior to the diencephalon supply the different organs of the body o Functions in coordinating responses to visual o Some cranial nerves are purely motor, some are inputs. purely sensory, while others are mixed. Cranial nerves III (oculomotor nerve) and IV (trochlear Each cranial nerve originates from the vein through nerve) two roots: o Emerge from the midbrain o Dorsal root o Ventral root o Note: these two do not unit with each other and HINDBRAIN look like separate nerves Description: Consists of the cerebellum (metencephalon) CN 11 & CN 12 and medulla oblongata (myelencephalon) o Additional nerves present in humans Cerebellum (metencephalon) o CN 11 (Accessory nerve) - controls the movement o Rudimentary, narrow, transverse gland lying of certain neck muscles dorsally, immediately behind the optic lobe o CN 12 (Hypoglossal nerve) - enables tongue o a depressed ridge immediately posterior to the optic movement lobes Different cranial nerves of the frog: o Controls of the mechanism of automatic movements of the body 1. CN 01 (Olfactory nerve) o Brings about coordination and movements of Arises from the anterior end of the olfactory locomotion lobe o Regulates complex muscular movements of the Innervates the cells of the olfactory sac Sensory in nature body o functions in balance. 2. CN 02 (Optic nerve) Medulla oblongata (myelencephalon) Arise from the retina of the eye o seen as an inverted triangle that tapers posteriorly. Purely sensory o Widening of the spinal cord o posterior to the cerebellum 3. CN 03 (Oculomotor nerve) o An important nerve center Small nerve arising from the ventral side of o Has nerve centers of all different functions the midbrain o regulates most visceral functions. Divides into branches which supply the o 4th ventricle - cavity of the myelencephalon that is anterior, superior, and interior recti muscles also triangular and the interior oblique muscles of the eye o Seven/six pairs of cranial nerves arise from the Excusively motor sides of the medulla oblongata ➔ CN V (trigeminal) 4. CN 04 (Trochlear nerve) ➔ CN VI (abducens) Small nerve arising from the dorsal side of ➔ CN VII (facial) the brain, between the optic lobes of the ➔ CN VIII (auditory) cerebellum ➔ IX (glossopharyngeal) Close to the superior oblique muscles of the eye DO | BLOCK05191D 19  panindigan mo ‘yan beh pinili mo ‘yan Exclusively motor 5. CN 05 (Trigeminal nerve) Largest of the cranial nerves Arises from the anterior end of the medulla oblongata Divides into three branches ○ Ophthalmic superficialis - sensory ○ Mandibular - sensory ○ Maxillary - motor Mixed nerve 6. CN 06 (Abducens nerve) Arises from the ventral side of the medulla oblongata Enters the orbit and goes to the posterior rectus muscle of the eye Motor nerve 7. CN 07 (Facial nerve) Has both visceral sensory and visceral motor PERIPHERAL NERVOUS SYSTEM fibers Divided into two branches ○ Palatine - goes to the roof of the buccal cavity ○ Hyomandibular - goes to the tongue and muscles of the jaw Mixed nerve 8. CN 08 (Auditory nerve) Arises from the medulla oblongata Goes to the internal ear Sensory 9. CN 09 (Glossopharyngeal nerve) Arises from the lateral side of the medulla oblongata Goes to the tongue, hyoid, and pharynx Mixed nerve 10. CN 10 (Vagus nerve) Arises from the lateral side of the medulla oblongata Description: includes nerves arising from the brain and Goes as a visceral branch to the larynx, spinal cord esophagus, stomach, gastric, heart, and o Cranial nerves - arise directly from the brain lungs o Spinal nerves - arise from the spinal cord Mixed nerve Nerve: o Solid structures that look like white threads o May be afferent (sensory), efferent (motor), or both Sensory nerve fibers o Those that carry impulses from the receptors to the CNS Motor nerve fibers o carry impulses of appropriate order from CNS to effector organs DO | BLOCK05191D 20  panindigan mo ‘yan beh pinili mo ‘yan REFERENCES Notes from the discussion by Ms. Jaryna Limbauan De La Salle University Powerpoint Presentation SPINAL CORD Description: Posterior to the medulla oblongata Functions: o Links the brain and most parts of the body o Spinal reflex actions o an elongated cylindrical structure and tapers posteriorly. Reflex o involuntary, predictable response to a stimulus. Has two enlargements: o Brachial enlargement - at the level of the arms and shoulder o Lumbas enlargement - found at the posterior aspect of the trunk o These enlargements represent aggregates of nerve supplying the forelimbs and hindlimbs, respectively. Filum o The pointed end of the spinal cord o is housed within the neural canal of the urostyle. Roots of the spinal nerves o Towards the posterior end of the spinal cord, the roots tend to crowd themselves and together with the filum terminale, they appear like horse’s tail, thus referred to as cauda equina. Central canal o cavity of the spinal cord. Ventricles o cavities of the brain DO | BLOCK05191D 21