Respiratory System Lecture Notes - Assuit University PDF

BLOCK RRS-209 Respiratory - Renal System Lecture Respiratory System Ass. Prof. Dr. Safaa Said Department of Histology &Cell Biology Assuit University  Learning objectives...

BLOCK RRS-209 Respiratory - Renal System Lecture Respiratory System Ass. Prof. Dr. Safaa Said Department of Histology &Cell Biology Assuit University  Learning objectives Know the different classifications of Correlate functions of the After this lecture, students should be the respiratory tract: - Conducting conducting & respiratory able to: and respiratory portions. portions with histological structure. Compare between the histological structure of the trachea, bronchi, bronchioles, alveoli and discriminate Discriminate the type of the lining the type of their lining epithelium. epithelium of the respiratory system Describe the histological structure of Clara (club) cell and identify its function Conducting & respiratory portions of the Respiratory tract The conducting portion: The respiratory portion: {does not participate in gas (Lung parenchyma), exchange} consists of nasal participates in gas exchange cavity, paranasal sinuses, consists of respiratory nasopharynx, larynx, trachea, bronchioles, alveolar ducts, bronchi and bronchioles that alveolar sacs and alveoli. further divide into terminal bronchioles.  Nasal Cavity The nose moistens, warms inhaled air & preventing particulate matter from entering the airways. It is playing an important role in the sense of smell. The left and right nasal cavities each have two components: the external dilated vestibule and the internal nasal cavity. Air enters the nose through the anterior nares (nostrils), passing the 3 anterior nasal hairs (vibrissae); these trap and prevent inhalation of larger foreign particles. The epithelial lining changes shortly after entering the nose from keratinized to respiratory epithelium. Olfactory epithelium, possess receptors that bind specific odorants, is found in the upper regions of the nasal airway above the superior conchae and is specialized for the detection of smell  Anterior portion of the nasal cavity (vestibule): The vestibule is lined with skin and has vibrissae; short stiff hairs that prevent larger particles from entering the nasal cavity. The dermis contains 1- NASAL numerous sebaceous and sweat glands. CAVITY Posterior portion of the nasal cavity: - Except for the vestibule and olfactory region, the nasal cavity is lined by pseudostratified ciliated columnar epithelium, frequently called respiratory epithelium.  The subepithelial C.T. (Lamina propria) is richly vascularized. It has many seromucous glands and abundant lymphoid elements, including occasional lymphoid nodules. Olfactory region of the nasal cavity: Site: it is located in the roof of the nasal cavity, the superior aspect of the nasal septum and the superior conchae. Olfactory epithelium: It is yellow in the living person (due to the presence of pigment in the epithelium) and responsible for perception of odours. Olfactory epithelium is composed of 3 types of cells: olfactory, sustentacular and basal cells.  Olfactory epithelium: Supporting cells: LM:They are tall columnar cells with fine yellowish granules in their cytoplasm that responsible for the yellowish color of the mucosa. The nucleus is oval and situated at the superficial portion of cytoplasm. Their free cell surface presents microvilli that covered with a thin film of serous fluid produced from the Bowman´s glands. They joined with adjacent olfactory cells by junctional complexes to prevent separation of the cells and access of secretion. They have a supporting and nourishment function for olfactory cells.  b. Olfactory (chemoreceptor) cells They are bipolar neurons which lie in-between the supporting cells. They have oval or rounded cell body contain spherical nucleus, apical dendrite and basal unmyelinated axons directed to the olfactory bulb. The nucleus is roundish and present in the widest part of the body. The cytoplasm is more electron lucent than that of the other types of cells, and contains moderate RER, and moderate supra-nuclear Golgi. Most of organelles are close to the nucleus. The apical dendrite is modified to form a roundish olfactory vesicle projecting above the surface of sustentacular cells.  Long, non motile (lacking the dynein) olfactory cilia (6-8 cilia) extend from the olfactory vesicles which act as receptors. They are stimulated by odoriferous substance dissolved in serous secretions bathing olfactory cilia. The axon of olfactory cells penetrates the basal lamina and join together to form bundles of nerve fibers. The nerve fibers penetrate the cribriform plate of ethmoid in the roof of the nasal cavity to synapse with 2ry neurons in the olfactory  c. Basal (reserve or stem) cells They are small rounded cells located close to the basal lamina. Their nuclei are small darkly stained frequently invaginated. It lie on the basement membrane forming a single layer at the base of the epithelium. The cytoplasm contains few organelles, a feature consistent with their role as reserve cell. They can be differentiated to form olfactory or sustentacular cells (during prenatal life). The neurons are not replaced at postnatal life. b. Lamina propria: ► Formed of dense fibro-elastic connective tissue that contains serous glands (Bowman´s glands). Their secretion covers the olfactory cilia to clear them and thus allow perception of new odorous substances.  PARANASAL SINUSES - Ethmoid, sphenoid, frontal and maxillary bones of the skull contain large paranasal sinuses which communicate with the nasal cavity. - They are lined with a thin mucous membrane, the epithelium of which is pseudostratified columnar ciliated epithelium with goblet cells. - The cilia sweep the mucous layer toward the nasal cavity.  3- NASOPHARYNX The nasopharynx is the area behind the nose and above the soft palate. Its nasal side is lined by a respiratory epithelium. Its oral surface is lined with stratified squamous epithelium. It is protected from the regurgitation of food during swallowing by the soft palate rising upwards and closing it off from the rest of the pharynx. The lamina propria of the posterior aspect of the nasopharynx contains the pharyngeal tonsils. The pharyngeal tonsil (a collection of lymphoid tissue commonly known as the adenoids) is found in the posterior wall and roof of the nasopharynx. The eustachian tube, a conduit with the middle ear, enters at the level of the floor of the nose on the lateral walls. This explains the common concurrence of throat and middle ear infections.  4- LARYNX It is a musculocartilaginous structure situated between the pharynx and the trachea, acts as an airway sphincter during swallowing and contains the vocal cords which are responsible for sound (vocalization). The laryngeal wall is composed of a mucosa, cartilages and striated muscle fibers in C.T. sheath. Its wall is reinforced by cartilages (thyroid, cricoids, epiglottis, and paired corniculate and cuneiform arytenoids) with ligaments and muscles that regulate the size of the laryngeal inlet.  The thyroid, cricoid and lower parts of arytenoids are hyaline cartilages. The epiglottis, corniculate, cuneiform and vocal processes of arytenoids are elastic cartilages The epiglottis is an elastic flap of cartilage, which lies behind the tongue and forms the entrance to the larynx. It serves to prevent swallowed food or fluid from entering that passage. The mucosa of the anterior surface of epiglottis & vocal cords is nonkeratinized stratified squamous epithelium while the rest of the larynx is lined with respiratory epithelium  Trachea The tracheais a tube lies between the The trachea is lined withrespiratory larynx and main bronchi of the lungs. epithelium, which acts as an It has a series of20 C-shaped hyaline escalator, wafting particulate matter cartilagerings that keep the tracheal in the mucus upwards, away from the lumen open with aband of smooth lower airways.The elastic fibersin the muscle(trachealis muscle) over the lamina propria prevent excessive cartilage-deficient distention of the lumen.The lamina areaposteriorly(i.e. against the propria containsnumerous esophagus) seromucous (mixed) glands.  The wall of the trachea consists of 3 definable layers: 1. Mucosa: A- Epithelium: Respiratory epithelium (pseudostratified columnar ciliated with goblet cells). six types of cells could be recognized: ciliated columnar cells, goblet cells, basal cells, brush cells, serous cells and kulchitsky (K) or small granule cells. B- The lamina propria: Loose fibroelastic CT rich in elastic fibers, lymphocytes, and lymphatic nodules. C. Lamina elastic interna: The elastic fibers are condensed to form an elastic membrane separating the lamina propria from the submucosa. It is responsible for elastic recoil of the trachea after expiration. 2. Sub-mucosa: CT layer which contains mixed glands. Their ducts pass through the elastic membrane to open onto the surface. 3- Fibro-cartilagenous layer: Fibroelastic CT containing 20 C-shaped hyaline cartilaginous rings located anteriorly and laterally, but incomplete posteriorly. Posteriorly, the wall of the trachea contains a thick band of transversely arranged bundles of smooth muscles.  Respiratory epithelium It is characteristically pseudostratified columnar ciliated with goblet cells. This epithelium has five major cell types: 1- Ciliated columnar cells. 2- Goblet cells. 3- Basal cells. 4- Brush cells. 5- Pulmonary neuroendocrine cells  Respiratory System Ciliated columnar cells and Goblet cells The beating motion of the cilia and the mucous secretion of the goblet cells make up the “mucociliary escalator” which is important in removing the inhaled particles. This is an important defense against the  Pulmonary neurendocrine cells (PNECs) or Kulchitsky (K) or small granule cells They are argentaffinlike cells, resemble the enteroendocrine cells of GIT. They have neuro-endocrine function, secrete peptides and endocrine factors that may play role in sensing low tissue oxygen and inducing lung growth and repair. PNEC hyperplasia lead to small cell lung cancer, is thought to be induced by nicotine. The respiratory epithelium of people chronically REFERENCES: JUNQUEIRA’S BASIC ELSEVIER’S INTEGRATED HISTOLOGY (TEXT AND ATLAS) HISTOLOGY (2007) 1STEDITION. (2018) 15 TH EDITION.  Choose the correct answer 1- T.S. of the trachea reveals: a. Multiple plates of cartilage. b. No cartilage. c. C-shaped elastic cartilage rings. QUIZ d. Compact bone. e. C-shaped hyaline cartilage rings. 2- The smooth muscle fibers of the trachea are present: a. In the submucosa. b. Between the cartilage ends. c. In the mucosa. d. Over the cartilage-deficient area anteriorly. e. Around the lumen