Ebook Histology text and atlas: Part 2

(BQ) Part 2 book Histology text and atlas presents the following contents: Bone, nervous tissue, muscle tissue, circulatory system, lymphoid (immune) system, oral cavity, gastrointestinal tract, accessory glands of the gastrointestinal tract, respiratory system, urinary system, male reproductive system,...

Senior Commissioning Editor: P Sangeetha Development Editor: Dr Alpna Rastogi Production Editor: Divya Ganesan Compositor: Idesign Manager Manu acturing: Anil Kumar Gauniyal Copyright © 2013 by Wolters Kluwer Health (India) 10th Floor, ower C Building No 10 Phase – II DLF Cyber City Gurgaon Haryana - 122002 All rights reserved T is book is protected by copyright No part o this book may be reproduced in any orm or by any means, including photocopying, or utilized by any in ormation storage and retrieval system without written permission rom the copyright owner T e publisher is not responsible (as a matter o product liability, negligence, or otherwise) or any injury resulting rom any material contained herein T is publication contains in ormation relating to histology that should not be construed as speci c instructions or individual patients Manu acturers’ product in ormation and package inserts should be reviewed or current in ormation, including contraindications, dosages, and precautions All products/brands/names/processes cited in this book are the properties o their respective owners Re erence herein to any speci c commercial products, processes, or services by trade name, trademark, manu acturer, or otherwise is purely or academic purposes and does not constitute or imply endorsement, recommendation, or avoring by the publisher T e views and opinions o authors expressed herein not necessarily state or ref ect those o the publisher and shall not be used or advertising or product endorsement purposes Care has been taken to rm the accuracy o the in ormation presented and to describe generally accepted practices However, the authors, editors, and publishers are not responsible or errors or omissions or or any consequences rom application o the in ormation in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy o the contents o the publication Application o this in ormation in a particular situation remains the pro essional responsibility o the practitioner Readers are urged to rm that the in ormation, especially with regard to drug dose/usage, complies with current legislation and standards o practice Please consult ull prescribing in ormation be ore issuing prescription or any product mentioned in the publication T e publishers have made every e ort to trace copyright holders or borrowed material I they have inadvertently overlooked any, they will be pleased to make the necessary arrangements at the f rst opportunity First Edition, 2013 ISBN-13: 978-81-8473-508-6 Published by Wolters Kluwer (India) Pvt Ltd., New Delhi Printed and bound at Sanat Printers, Haryana For product enquiry, plea se contact – Marketing Department (marketing@wolterskluwerindia co.in) or log on to our website www.wolterskluwerindia co.in Dedica ted To my late ather, whose hard work and sacrif ce enabled me to succeed in all that I have endeavoured To my brother, who took over all the responsibilities a ter our ather passed away To my mother, or her unwavering support and pro ound devotion and To my students, or always keeping me on my toes Preface T is book is a result o persistent eedback received rom several o my students about the di culties aced by them in understanding histology T e most common concerns related to understanding and replicating the diagrams correctly, dif erentiating between similar looking slides and getting a sound grasp o the conceptual details It was to address these concerns that I took up the project o writing this book I have endeavoured to resolve the above-mentioned di culties by presenting histology in a simple, interesting and lucid manner I hope this will make it easier or students to understand and retain concepts as well as to reproduce the diagrams in their practical manuals T e book caters primarily to the requirements o undergraduate medical and dental students Pathology students will also nd the book use ul or re reshing histology undamentals Some o the key eatures o the book are as ollows: T e Diagrams T ere are 118 coloured diagrams o histological slides T ese simple, clear, well-labelled, hand-drawn diagrams will help the students in identi cation o the slides T ey can be easily reproduced by them in the practical manuals Important diagrams are also supported by relevant slides T e 186 line diagrams and three-dimensional illustrations given in the book will urther aid understanding and retention T e ext Based on the eedback given by an overwhelming majority o students, the text has been presented in a crisp, bulleted ormat T e in ormation ows rom basic to detailed with proper structuring in terms o headings and subheadings to enable easy comprehension Identif cation o Similar Looking Slides T e book has 83 coloured photomicrographs (PMGs) o most o the organs Studying these pictures will make the identi cation o actual histological slides easier or the students Similar looking slides have been compared and their dif erentiating points have been enumerated separately in the text Functional and Clinical Correlations Several unctional and clinical correlations have been mentioned T ese not only make the topic interesting, but also help the students in understanding the importance o histology in the identi cation, diagnosis and pathogenesis o diseases viii Preface Key Points At the end of each chapter, there are key points corresponding to the text and diagrams T ese key points will enable a quick revision of the subject by the students It has taken me six years of hard work to bring forth this book to you I hope that it will meet the expectations of my colleagues and requirements of the students I shall welcome feedback for further improvement of the book T ank you for choosing to read this book Brijesh Kumar histology.by.brijesh@gmail.com CHAPTER 15 Respiratory System ● ● ● ● ● T e structures which are responsible for the inhalation of air, exchange of gases between the air and blood and exhalation of carbon dioxide constitute the respiratory system Apart from respiration, this system is also responsible for olfaction and sound production T e respiratory system consists of two parts—a conducting part (which carries air) and a respiratory part (where gas exchange takes place) T e conducting part consists of nasal cavity, paranasal sinuses, nasopharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles (Fig 15.1) T e respiratory part consists of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli Na s a l cavity Na s opha rynx Pa la te Ora l cavity Tongue Epiglottis Tra che a Oe s opha gus P rincipa l bronchus Lung Lung Figure 15.1 Conducting part of the respiratory system RESPIRATORY TRACT ● ● T e respiratory tract begins from the nasal cavity From the nasal cavity air enters the nasopharynx, the larynx and then into the trachea From the trachea, the air enters the bronchial tree Paranasal sinuses open in each nasal cavity Chapte r Respiratory System 219 BRONCHIAL TREE (Fig 15.2) ● ● T e bronchial tree begins with the bifurcation of the trachea and undergoes extensive branching As the bronchial tree divides, the size of lumen decreases and there is enormous increase in the surface area for the gaseous exchange T e trachea divides into two primary or principal bronchi (singular: bronchus), one for each lung Tra che a Ca rtila ge ring P rima ry bronchus S e conda ry bronchus Ca rtila ge pla te S pira lly a rra nge d s mooth mus cle s Te rtia ry bronchus Te rtia ry bronchus Bronchiole Bronchiole Blood ve s s e l a round a lve oli Alve oli Re s pira tory bronchiole Te rmina l bronchiole Alve ola r duct Alve ola r s a c Figure 15.2 Schematic diagram of the respiratory tree Re s pira tory bronchiole 220 ● ● ● ● ● ● ● Histology: Text and Atlas T e primary bronchus enters the lung and divides into secondary or lobar bronchi, one or each lobe (three or the right lung and two or the le t lung) Secondary bronchi divide into numerous tertiary or segmental bronchi, each aerating its own territory in a lobe o the lungs (Fig 15.2) T e tertiary bronchi divide into numerous bronchioles which urther divide into smaller bronchioles T e smallest bronchioles in airways are called terminal bronchioles T e conducting part o the respiratory tract ends at the terminal bronchioles, and airways distal to this constitute the respiratory part (though it is called respiratory part, it also conducts air) (Fig 15.2) T e terminal bronchiole divides and gives rise to respiratory bronchioles T e wall o respiratory bronchiole shows outpouchings, the alveoli (singular: alveolus), in which gaseous exchange takes place, and hence it is called respiratory bronchiole As the respiratory bronchiole divides, there is a gradual increase in the number o alveoli in the distal airways Respiratory bronchioles open into the alveolar duct In the wall o the alveolar duct, the number o alveoli increases so much that they lie adjacent to one another T e walls o alveolar ducts appear to be entirely o alveoli (Fig 15.2) Alveolar ducts open into the alveolar sacs (Fig 15.2), which are clusters o alveoli GENERAL FEATURES OF THE WALL T e walls o dif erent parts o the respiratory tract show dif erent eatures In general, the wall o the respiratory tract consists o the ollowing ( rom lumen to outside): Epithelium Lamina propria Layer o smooth muscles Submucosa Cartilage Adventitia (See Figs 15.6 and 15.7 or histological components o the respiratory tract.) ● ● ● ● ● ● Re spirato ry Epithe lium It is ciliated pseudostratif ed columnar epithelium with goblet cells T ere is a gradual decrease in the height o the epithelial cells in distal airways T e epithelium loses goblet cells and cilia as it approaches the terminal parts o the tract Goblet cells secrete mucus on the sur ace o the epithelium, and this mucus traps the inhaled particles T e cilia o the epithelial cells beat towards the pharynx, and they propel the mucus present on the sur ace o the cell towards the pharynx From the pharynx, mucus is coughed out or swallowed T e respiratory epithelium has some more types o cells Short or ba sal cells are the stem cells which divide and dif erentiate into the other types o cells present in the respiratory epithelium Neuroendocrine cells are small cells scattered among the other cells o the epithelium, and these cells secrete serotonin ● ● ● Lamina Pro pria It is present underneath the epithelium and consists o loose connective tissue In some regions, it has lymphoid nodules and mucous glands too Respiratory epithelium along with lamina propria is called respiratory mucosa Smo o th Muscle s A layer o smooth muscle is present underneath the lamina propria It is seen in the airway distal to the trachea, till the alveolar duct Bundles o smooth muscles are spirally arranged ● Chapte r ● Respiratory System 221 T e unction o these muscles is to regulate the diameter (and resistance) o the airways Parasympathetic stimulation o these muscles constricts airway passages, thereby increasing the airway resistance Sympathetic stimulation dilates airways and decreases airway resistance Submuco sa It is a layer o connective tissue, and it has mucous and serous glands T e ducts o these glands open into the lumen o the airways Gradually, the presence o these glands decreases in the distal airway; they are seen till tertiary bronchi Cartilag e Underneath the submucosa, hyaline cartilage is present to support the wall o the airways It prevents the airways rom collapsing It is present till tertiary bronchi Adve ntitia It is the outermost layer, which consists o connective tissue, and it blends with the surrounding tissues NASAL CAVITY ● ● ● T ere are two nasal cavities separated by the nasal septum Structurally and unctionally, each cavity has three regions—vestibule, respiratory region and ol actory region (Fig 15.3) T e entrance o the nasal cavity is called vestibule It is lined by skin (keratinised stratif ed squamous epithelium) having sebaceous and sweat glands and short thick hairs called vibrissae (Fig 15.3) Behind the vestibule, there is the respiratory region o the nasal cavity; it is lined by the respiratory mucosa Fronta l s inus P ituita ry fos s a Olfa ctory e pithe lium S phe noid s inus Ve s tibule Vibris s a e Ha rd pa la te S oft pa la te Tongue Ante rior s urfa ce P rynx Epiglottis Pos te rior s urfa ce Ve s tibula r fold Voca l fold Figure 15.3 Sagittal section of the nasal cavity, pharynx and larynx Oe s opha gus 222 ● ● Histology: Text and Atlas T e ol actory region is in the upper part o the nasal cavity; it is lined by ol actory epithelium which is pseudostratif ed columnar epithelium T e lamina propria o the nasal mucosa contains numerous seromucous glands; secretions o these glands add moisture to the inspired air Olfacto ry Epithe lium (Fig 15.4) ● ● ● ● ● ● It is responsible or the sense o smell It has three types o cells—supporting sustentacular cells, basal cells and ol actory cells Supporting cells are tall with microvilli on their ree sur ace Basal cells are small, and they not reach the sur ace Ol actory cells are bipolar neurons T e apex o an ol actory cell expands to orm the ol actory vesicle, and numerous non-motile cilia arise rom it T e axons o the ol actory cells collect into bundles in the lamina propria Lamina propria o ol actory epithelium has Bowman’s glands Watery secretions o these glands around the cilia provide a liquid medium into which ol actory substance dissolves Ciliaa Microvilli S upporting ce ll Olfa ctory ce ll O Ba s a l ce ll Axons of the A oolfa ctory ce lls Figure 15.4 Olfactory epithelium PARANASAL SINUSES ● ● ● ● Paranasal sinuses are air-f lled spaces in the bones around the nasal cavity T ere are our pairs o paranasal sinuses—frontal, sphenoidal, ethmoidal and ma xillary; they are present in the bones with the corresponding names T ey open into the nasal cavity T ey are lined by the respiratory mucosa PHARYNX ● ● ● ● T e pharynx is a muscular tube which serves as a common passage or the respiratory and gastrointestinal tracts It lies behind the nasal and oral cavities and the larynx (Fig 15.3) It consists o three parts—nasopharynx, oropharynx and laryngopharynx T e wall o the pharynx consists o three layers—inner (luminal) mucosa, middle muscular and outer adventitia T e lining epithelium o the nasopharynx is the respiratory epithelium T e walls o the oropharynx and laryngopharynx are subjected to mechanical injury during the swallowing o ood; hence, these parts are lined by non-keratinised stratif ed squamous epithelium Chapte r ● Respiratory System 223 Underneath the epithelium, there is the lamina propria which consists o connective tissue In the lamina propria, numerous salivary glands are present; ducts o these glands open into the lumen o the pharynx Numerous lymphoid tissues are also present in the lamina propria; these are mucosaassociated lymphoid tissue (MAL ), discussed in detail in Chapter 11 LARYNX ● ● ● ● ● T e larynx connects the oropharynx and the trachea It is the component o the conductive part o the respiratory system, and it is also responsible or sound production T e interior o the larynx has two olds—vestibular and vocal olds—projecting into the lumen (Fig 15.3) T e vestibular old ( alse vocal cord) is lined by respiratory epithelium Underneath the epithelium, in the lamina propria, there are numerous serous and mucous glands; the ducts o these glands open into the luminal sur ace o the larynx T e vocal old (true vocal cord) is lined by stratif ed squamous non-keratinised epithelium which provides protection rom physical injury during its movement T e remaining parts o the interior o the larynx are lined by the respiratory mucosa Underneath the lamina propria, laryngeal cartilages are present T ese are thyroid, cricoid, epiglottis, corniculate and cunei orm cartilages; they are present in the wall o the larynx and orm its skeletal ramework T e thyroid, cricoid and most o arytenoid consist o hyaline cartilage whereas the epiglottis, corniculate and tips o the arytenoid are elastic cartilage Epig lo ttis (Fig 15.5; PMG 15.1) ● T e epiglottis has upper and lower ends, anterior and posterior sur aces and two lateral borders (Fig 15.3) (ii) Re s pira tory e pithe lium (i) Ta s te bud S tra tifie d s qua mous non-ke tinis e d e pithe lium Ela s tic ca rtila ge P e richondrium La mina propria S e romucous gla nds Lingua l s urfa ce (cove re d by s tra tifie d s qua mous non-ke tinis e d e pithe lium) Figure 15.5 Section o epiglottis in low magnif cation Inset (i) shows an enlarged view o taste bud Inset (ii) shows junction o ciliated pseudostratif ed columnar epithelium (respiratory) and stratif ed squamous nonkeratinised epithelium (H&E pencil drawing) 224 Histology: Text and Atlas Lingua l s urfa ce —cove re d by s tra tifie d s qua mous non-ke tinis e d e pithe lium La mina propria S e romucous gla nds P e richondrium Ela s tic ca rtila ge PMG 15.1 Epiglottis (H&E stain, X5) ● ● ● he lingual surface (or anterior surface) and upper part of the lar yngeal surface (or posterior surface) are covered by stratified squamous non-keratinised epithelium, and the rest of the lar yngeal surface is covered by respirator y epithelium he upper part of the lar yngeal surface, where the epithelium is stratified squamous non-keratinised, shows the presence of some taste buds Lamina propria consists of connective tissue with numerous serous and mucous glands Elastic cartilage is present underneath the lamina propria and provides the skeletal framework to the epiglottis TRACHEA (Fig 15.6; PMG 15.2 and 15.3) ● ● ● ● T e luminal surface of the trachea is lined by respiratory epithelium Lamina propria is present underneath the epithelium Underneath the lamina propria, there is the submucosa with serous and mucous glands; the ducts of these glands open on the luminal surface of the epithelium Beneath the submucosa, there is ‘C’-shaped hyaline cartilage T e ends of the ‘C’-shaped cartilage are on the posterior aspect of the trachea T e two ends of these cartilages are joined by smooth muscle called trachealis (Fig 15.6) Chapte r S ubmucos a Respiratory System S e romucous gla nds in s ubmucos a Mucos a Ca rtila ge Tra che a lis mus cle Adve ntitia Re s pira tory e pithe lium S e romucous gla nds in s ubmucos a Goble t ce ll La mina propria P e richondrium Ca rtila ge Adventitia Figure 15.6 Section o trachea in low magnif cation Inset shows part o trachea in high magnif cation (H&E pencil drawing) 225 226 Histology: Text and Atlas Re s pira tory e pithe lium La mina propria S ubmucos a Ca rtila ge PMG 15.2 Trachea (H&E stain, X10) Brus h borde r Goble t ce ll La mina propria PMG 15.3 Respiratory epithelium of the trachea (H&E stain, X40) LUNGS Like any other organ, lungs also consist o parenchyma and stroma T e airways inside the lungs constitute the parenchyma, whereas the connective tissue around the airways constitute the stroma o the lungs Primary o r Principal Bro nchus (Fig 15.2) T e primary bronchus is similar to the trachea with a ew dif erences which are as ollows: T e cells o respiratory epithelium are shorter and have less number o goblet cells Between the lamina propria and the submucosa, there are bundles o spirally arranged smooth muscle, completely encircling the bronchus Glands in submucosa are less in number compared to those in the submucosa o trachea Cartilaginous rings completely encircle the bronchus ● ● ● ● Chapte r Respiratory System Se co ndary and Te rtiary Bro nchi (Figs 15.2 and 15.7; PMG 15.4) T ey are similar to the primary bronchus except for the following: T e number of goblet cells is further reduced in the epithelium T e number of glands in the submucosa is also reduced T e cartilage is present as irregular plates ● ● ● S mooth mus cle s Ca rtila ge pla te s Re s pira tory e pithe lium La mina propria S ubmucos a PMG 15.4 Intrapulmonary bronchus (H&E stain, X10) Bro nchio le (Figs 15.2 and 15.7; PMG 15.5) ● ● ● ● ● T e epithelium is ciliated, simple columnar or cuboidal erminal bronchiole is devoid of goblet cells It has no glands It has no cartilage T e smooth muscles are very prominent here Re s pira tory e pithe lium S mooth mus cle s PMG 15.5 Bronchiole (H&E stain, X5) 227 228 Histology: Text and Atlas Alve ola r s a c Bronchiole Alve olus Alve ola r duct Re s pira tory bronchiole Alve ola r s a c Lymphoid nodule P ulmona ry a rte ry Bronchiole Intra pulmona ry bronchus Te rmina l bronchiole S mooth mus cle s a rra nge d s pira lly (a ) Adve ntitia Ca rtila ge pla te La mina propria Re s pira tory e pithe lium S mooth mus cle s a rra nge d s pira lly S e romucous gla nds S ubmucos a (b) Figure 15.7 Section o (a) lungs in low magnif cation and (b) intrapulmonary bronchi in medium magnif cation (H&E pencil drawing) Chapte r ● Respiratory System 229 In the epithelium of the terminal bronchiole, dome-shaped cells called Cla cells are also present, whose function is not known hey may provide some protection against inhaled toxins and carcinogens Re sp irat o ry Bro n ch io le (Figs 15.2 and 15.7; PMG 15.6) ● ● ● ● T e respiratory bronchiole is lined by simple cuboidal epithelium; these cells lack cilia Goblet cells are absent Epithelium is interrupted by alveoli, and at the opening of the alveoli the epithelium changes to simple squamous epithelium T e smooth muscle forms a ring around the opening of the alveoli Alve ola r s a c Re s pira tory bronchiole Alve ola r duct Alve oli ope ning S mooth mus cle Alve oli Blood ve s s e l PMG 15.6 Section of lung showing respiratory bronchiole and alveolar duct (H&E stain, X10) Alve o lar Duct (Figs 15.2 and 15.7; PMG 15.6) ● ● ● T e wall of the alveolar duct consists of alveoli, lined by simple squamous epithelium Underneath the epithelium, smooth muscles form rings at the opening of the alveolar sacs and alveoli, which are seen as a small bulge, in the wall in between two adjacent alveoli Smooth muscles disappear in the terminal parts of alveolar ducts Alve o lar Sac and Alve o li ● ● ● T e alveolar duct opens into dead end sacs, the alveolar sacs, which have openings of the alveoli (Figs 15.2 and 15.7; PMG 15.6) Alveoli increase the surface area for the gaseous exchange Alveoli are surrounded by a network of capillaries (Fig 15.2) T e gaseous exchange occurs between the air present in the alveoli and the blood in the capillaries across their walls (see ‘Interalveolar Septum’) Alveoli are thin-walled outpouchings, lined by a single layer of cells; these cells are of two types: type I and type II cells, also called pneumocytes or alveolar cells See Figure 15.8 for illustration of pneumocytes 230 Histology: Text and Atlas Typ e I Pn e u m o cyt e s ● ● ● T ese cells are squamous epithelial cells; adjacent cells are joined together by tight junctions T ey cover most o the alveolar sur ace T ese cells are involved in gaseous exchange Typ e II Pn e u m o cyt e s ● ● ● T ese are cuboidal cells, scattered among type I cells Compared to type I cells, their contribution to alveolar sur ace is very small T ese cells are secretory cells T ey secrete pulmonary sur actant, which lowers the sur ace tension and prevents alveoli rom collapsing Although the number o type I and type II cells is almost equal, type I cells orm 90– 95% o alveolar sur ace and type II cells contribute 5– 10% o alveolar sur ace only T e small contribution to alveolar area by type II cells is due to their shape Inte ralve o lar Se ptum ● ● ● ● ● It is the wall present in between the two adjacent alveoli (Fig 15.8) It consists o epithelial cells o each alveolus on both sides, with connective tissue sandwiched between them Capillaries are present in the connective tissue Apart rom the capillaries, the connective tissue in the interalveolar septum contains collagen and elastic f bres, f broblasts and macrophages (dust cells) At some places, the capillary comes in contact with the alveolar sur ace At these sites, the basement membrane o the capillary and the alveolus use (Fig 15.8); this is the site o gaseous exchange T e interalveolar septa has numerous alveolar pores (pores o Kohn), which allow equalisation o pressure between the adjacent alveoli Type II pne umocyte Type I pne umocyte Alve olus Alve olus Ba s e me nt me mbra ne Ca pilla ry Inte lve ola r s e ptum Endothe lium Conne ctive tis s ue Alve olus Fus e d ba s e me nt me mbra ne of the a lve olus a nd the ca pilla ry Figure 15.8 Interalveolar septum Re d blood corpus cle Chapte r Respiratory System 231 A ir–Blo o d Barrie r T e oxygen molecule present in the alveolus dif uses across the epithelial cells lining the alveolus, the used basement membrane o the alveolus and capillary, the endothelial cells o the capillary and nally into the red blood cell (Fig 15.8) PULMONARY CIRCULATION ● ● ● ● Lungs have dual blood supply through bronchial and pulmonary vessels Bronchial vessels supply the conducting part o the lungs and pulmonary vessels supply the respiratory part T e blood vessels accompany the airways; they are present in the connective tissue that is present around the airways At the level o the alveolar ducts, arterioles divide and orm a capillary network around alveoli T ese capillary networks are present in the interalveolar septum LYMPHATIC CIRCULATION ● ● Lymphatic vessels accompany the blood vessels No lymphatic vessels are present in the alveolar sac and interalveolar septa PLEURA ● ● ● ● Pleura is a serous sac which covers the lungs It consists o visceral and parietal layers Between the two layers is a potential space known as pleural cavity which contains pleural uid T e visceral layer lines the lungs and the parietal layer lines the interior o the thoracic cavity Histologically, pleura consists o mesothelium (simple squamous epithelium) overlying a thin layer o vascular connective tissue CLINICAL CORRELATES Emphysema ● It is characterised by abnormal permanent dilatation o airways distal to the terminal bronchiole Dilatations occur due to destruction o the walls o the airways Cigarette smoking and air pollution are the causative actors Bronchiectasis ● It is characterised by permanent dilatation o the bronchi and bronchioles due to damage to the muscles and elastic tissue Bronchial Asthma ● It occurs due to increased responsiveness o the airway to the allergen T e diameter o the airway is reduced due to contraction o the smooth muscles present in the airway Pulmonary Oedema ● It re ers to accumulation o uid within the lung parenchyma and air spaces o the lungs T e uid entering the alveoli o the lungs prevents gaseous exchange Pulmonary oedema is seen in le t ventricular ailure (it can occur in several other conditions also) when the le t ventricle ails to empty completely As a result backpressure develops in the le t atrium, pulmonary veins and capillaries Due to increase in capillary hydrostatic pressure, the uid moves rom the capillaries into the alveolar spaces 232 Histology: Text and Atlas KEY POINTS Epiglottis (Fig 15.5; PMG 15.1) ● ● ● Lingual sur ace and upper part o laryngeal sur ace are covered by stratif ed squamous nonkeratinised epithelium, and the rest o the laryngeal sur ace is covered by respiratory epithelium Lamina propria has numerous serous and mucous glands Elastic cartilage is present underneath the lamina propria Trachea and Bronchial Tree Part of the tract Trachea (Fig 15.6; PMG 15.2 and 15.3) Primary bronchus Conducting part Secondary and tertiary bronchi (Fig 15.7; PMG 15.4) Bronchiole (Fig 15.7; PMG 15.5) Epithelium ● ● ● ● ● Terminal bronchiole Respiratory bronchiole (Fig 15.7; PMG 15.6) ● ● ● ● ● Respiratory part Alveolar duct (Fig 15.7; PMG 15.6) Alveolar sac and alveoli (Figs 15.7 and 15.8; PMG 15.6) ● ● Smooth muscle Glands Cartilage Pseudostratif ed columnar epithelium with goblet cells Only on the posterior aspect, connecting the two ends o cartilage Numerous serous and mucous glands in submucosa ‘C’-shaped Cells are less taller Bundles o smooth muscles, present underneath the lamina propria; completely encircle the bronchus spirally Less in number as compared to trachea Cartilage completely encircles the bronchus Less number o goblet cells Same as primary bronchus Less number o glands Cartilage plates are present Ciliated simple columnar or cuboidal epithelium A ew goblet cells Very prominent Absent Absent Clara cells Very prominent Absent Absent Simple cuboidal epithelium No cilia No goblet cells Alveoli lined by simple squamous cells Arranged as a ring at the opening o the alveoli Absent Absent Wall has alveoli, lined by simple squamous epithelium Arranged as a ring at the opening o the alveolar duct and alveoli Absent Absent Type I and type II pneumocytes Absent Absent Absent cartilage, def cient posteriorly ... Vesicle 26 2 Bulbourethral Glands Penis 26 3 26 3 25 0 xvi Detailed Table of Contents Chapter 18 Female Reproductive System 26 6 Ovaries 26 7 Fallopian ube 27 1 Uterus 27 4 Cervix 27 7 Vagina 27 8 Mammary Gland... Gland 27 9 Chapter 19 Placenta and Umbilical Cord Placenta 28 7 Umbilical Cord 28 7 29 4 Chapter 20 T e Endocrine Glands 29 6 Pituitary Gland 29 6 T yroid Gland 303 Parathyroid Glands 307 Adrenal Glands... Pleura 23 1 21 8 Chapter 16 Urinary System Kidneys 23 4 Ureter 24 4 Urinary Bladder Urethra 24 7 21 8 23 4 24 6 Chapter 17 Male Reproductive System estis 25 1 Epididymis 25 7 Vas Deferens 25 8 Prostate 26 0