Benha University Faculty of Veterinary Medicine and Cytology Department Histology Exam

Time: - 3 hours تخلفات الفرقة الثانية June 2012 82

Please answer all following questions and illustrate your answers with diagrams مـــــن فضــــــــلك دعــــــم جمــــــيع اإلجـــــابات بالرســـوم التـوضــيحية

(I) Give short notes on:-

Hard Palate. In the fowl the lips and cheeks are replaced by the beak – an area of dense and horny lying over the mandible and incisive bones that serve as the bony foundation. There are no teeth. The so called egg tooth found on the end of the beak of newly hatched chickens is an aid to their escape from the egg at hatching and disappears after a day or two. The hard palate, forming the roof of the mouth, presents a long, narrow median slit that communicates with the nasal cavity (median – along the middle). The hard palate has five transverse rows of backwardly pointing, hard, conical papillae. Numerous ducts of the salivary pierce the hard palate to release their secretions into the mouth cavity Esophagus of poultry. I- Tunica mucosa of the esophagus: 1- Lamina epithelialis: was thrown into numerous longitudinal folds, variable in length The mucosal was a thick stratified squamous type non keratinized or incompletely kertinizied. The lining epithelium rested on a well-developed basement membrane. 2- The lamina propria was composed of connective tissue and rich in blood vessels, many collagen fibers and reticular fibers. It was, however, characterized by lack of elastic fibers and lymphoid tissue. Large simple branched alveolar glands were present. A tall columnar epithelium, whose cells contained flattened or oval basally situated nuclei, lined the mucus glands. This lining decreased to a cuboidal shape as it approached the surface. The esophageal glands were mucus in nature. The esophageal glands opened directly onto the surface epithelium through narrow clefts. 3- Lamina muscularis mucosa: - was composed of thick bundles of smooth muscle arranged longitudinally. The muscularis mucosae followed the folds of the mucus membrane. Esophagus of catfish. The esophagus of catfish was found to have numerous deep longitudinal folds. It was lined by a few layers of stratified squamous epithelium with numerous superficial mucous cells, so that it changed to simple columnar epithelium at the end of the esophagus. Taste buds were absent in the epithelium of the esophagus of catfish. The lamina propria was formed by loose connective tissue without elastic fibers. The lamina muscularis mucosa was not present. The tunica muscularis with striated muscular fibers had two layers; a thick inner circular and thinner outer longitudinal layer. Outer serosa was a thin layer of connective tissue surrounded by . The mucous cells were stained with AB and PAS in the lower part of the mucosal fold, but stained only with AB in the upper part of the mucosal folds, indicating the presence of neutral and acidic (carboxyl and sulphate groups) glycoprotein.

II- What do you know about:-

Trachea of duck. The avian trachea is similar to that of the mammals trachea T. mucosa: L. epith — with intraepithelial mucous L. prop. —fibro elastic C.T. containing mucous glands which may extend to the submucosa Tracheal rings, the trachea is supported by tracheal rings of hyaline cartilage, overlapping pattern are common. Ossification of the tracheal rings occurs in the trachea of geese and ducks. Tracheal muscles: — longitudinally oriented striated muscles are located at the lateral side of the tracheal rings The primary bronchi are similar to that of the avian trachea The cartilaginous rings are gradually replaced by dense collagenous CT The smooth muscle connect the free surface of the rings Proventriculus. The proventriculus is distinguished by its thick glandular mucous membrane. The glands secrete hydrochloric acid and pepsinogen (the precursor of pepsin). Tunica Mucosa: 1-Lamina Epithelialis:- The gastric epithelium of the proventriculus is simple columnar and mucus secreting cells. 2- Lamina propria:- A thin lamina propria separates it from the lobules of the submucosal glands and consists of thin loose connective tissue. These glands form an almost continuous mass of tissue, and penetrate the tunica submucosa also. With adjacent lobules separated by fine strands of connective tissue. Each gland lobule contains a central cavity with straight secretory tubules radiating to the interlobular connective, tissue. The glands contain only one type of cell, which secretes acid and pepsinogen, thus combining the functions of both the chief and parietal cells of the mammal. 3-Lamina muscularis mucosae:- It is thin layer and patches of smooth muscle fibers II-Tunica Submucosa: - It is loose connective tissue Tunica muscularis is arranged as inner circular and outer Longitudinal layers of smooth muscle. Tunica serosa: It is thin layer of loose connective tissue covered by flattened mesothelium. Gill arch. A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Many microscopic aquatic animals, and some that are larger but inactive, can absorb adequate oxygen through the entire surface of their bodies, and so can respire adequately without a gill. However, more complex or more active aquatic organisms usually require a gill or gills. Gills usually consist of thin filaments of tissue, branches, or slender tufted processes that have a highly folded surface to increase surface area. A high surface area is crucial to the gas exchange of aquatic organisms as water contains only a small fraction of the dissolved oxygen that air does. With the exception of some aquatic insects, the filaments and lamellae (folds) contain blood or coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body. Carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in various groups of aquatic animals, including mollusks, crustaceans, insects, fish, and amphibians. The gills of vertebrates typically develop in the walls of the pharynx, along a series of gill slits opening to the exterior. Most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange. When a fish breathes, it draws in a mouthful of water at regular intervals. Then it draws the sides of its throat together, forcing the water through the gill openings, so that it passes over the gills to the outside. Fish gill slits may be the evolutionary ancestors of the tonsils, thymus gland, and Eustachian tubes, as well as many other structures derived from the embryonic branchial pouches.

III- What are the histological structure of the following:-

Swim bladder. The swim bladder is made up of fibrosa, collagenase fiber walls and mucosa; its walls extend into the lumen to form dense respiratory alveoli, with the inner surface covered by a highly vascularized respiratory epithelium. The thin epithelial cells have the structural characteristics and function of type I and type II cells of lung alveoli in higher mammals. These cells and the endothelial cells compose the barrier through which gases must pass in the exchange between blood and air. Fundic gland region of tilapia. The sac-like stomach is divided into the cardiac, fundic, and pyloric regions. In the cardiac, region the folds are lined with a simple cubic epithelium and lamina propria that branch off and form small secondary folds. Mucous glands predominate in the lamina propria, which produce mucous to facilitate the passage of food. The muscular mucosa and submucosa are not evident. However, the muscular layer with the longitudinal tunica and the circular tunica is well developed. The last layer is a serous membrane with loose connective conjunctive tissue covered by a mesothelium. The gastric glands, when present, are always located in the lamina propria and not in the submucosa. The division of the stomach into three regions is based on the distribution of gastric glands and the presence and thickness of the mucosal folds. The mucosa of the pyloric stomach consists of a simple mucous secretory prismatic epithelial lining where the glands are formed by mucous secreting cells Gastric pits are located in the cardiac region and there is a gradual loss of glands in the fundic region. Three pyloric caeca are connected to the intestine after the pyloric region. The pyloric region contains only the lamina propria, which originates along with the primary and secondary epithelial folds in the stomach. The pyloric region is a nonglandular area. The muscularis mucosa is not well developed; The muscle layer of the stomach has an inner layer of smooth muscle fibers set in a circular arrangement and an outer layer of longitudinally placed fibers. The cardiac region of the stomach contains scattered skeletal striated fibers that may have originated in the esophageal region. The most developed muscle layer is found in the pyloric region. The serosa along the whole stomach is a thin dense connective tissue limited by a single layer of flat mesothelial cells. In the pyloric stomach, the serous membrane is continuous with the connective tissue of the serous sac that houses the pyloric caeca. Ureter of fish Epithelium---- Simple columnar L. Propria------Loose Ct T. Muscularis—Outer SMF T. Serosa------Loose Ct covered by mesothelium

**************************************** سوف يعقـــــد امتحـــان الشفــــــوي بعـد االمتحان النظري مباشـــــــــرة بالقســـــــم

GOOD LUCK Prof. Dr: Ihab M. A. EL-Zoghby Prof. of Histology and Head of Dept.