Histology Lab Finals 2024-2025 PDF

HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED LESSON 8: RESPIRATORY SYSTEM THE ALVEOLI The respiratory system provides for exchange of O2 and Alveoli, the cellular sites of the exchange of 02 and CO2...

HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED LESSON 8: RESPIRATORY SYSTEM THE ALVEOLI The respiratory system provides for exchange of O2 and Alveoli, the cellular sites of the exchange of 02 and CO2 CO2 to and from the blood. Respiratory organs include between inspired air and blood, are small, ar filled, the lungs and a branching system of bronchial tubes that saclike structures, which make up most of the lung link the sites of gas exchange with the external structure. (Keynote: gas exchange) They are lined by environment simple squamous epithelium to allow rapid diffusion of gases. The respiratory system has two functional components: ​ The conducting portion, which consists of the nasal cavities, pharynx, larynx, trachea, bronchi (Gr. bronchos, windpipe), bronchioles, and terminal bronchioles ○​ The conducting portion clean and humidifies inspired air and provides conduits for air movement to and from alveoli. ​ The respiratory portion, where the system's main function of gas exchange occurs, consists of respiratory bronchioles, alveolar ducts, and alveoli. THE ALVEOLAR DUCTS ​ Alveolar ducts are small airways in the lungs that connect the bronchioles to the alveolar sacs and alveoli where gas exchange occurs. These ducts play a crucial role in facilitating the flow of air from the bronchioles to the alveolar regions of the lungs for efficient gas exchange ​ They are located after the respiratory bronchioles and before the alveolar sacs. They serve as passageways between the conducting airways (bronchioles) and the respiratory units (alveoli). ​ They are lined by simple cuboidal epithelium in some areas and simple squamous epithelium where alveoli open directly into the ducts. The epithelium transitions from cuboidal to squamous as the ducts approach the alveoli. ★​ Key words: passageways, role in air conduction The Respiratory Epithelium 1 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED CELL TYPES IN THE ALVEOLI ​ Respiratory bronchioles - Simple cuboidal, ciliated cells and club cells, with scattered alveoli 1.​ Type I Alveolar Cells (Pneumocytes) - thin, flat ​ Alveolar ducts and sacs - Simple cuboidal between cells that cover about 95% of the alveolar surface many alveoli area, facilitating gas exchange between the air in ​ Alveoli - Types I and II alveolar cells (pneumocytes) the alveoli and the blood in the capillaries. 2.​ Type II Alveolar Cells (Pneumocytes) - Cuboidal cells scattered among the Type I cells producing surfactant which reduces surface tension, preventing alveolar collapse during exhalation. They also act as progenitor cells, regenerating both Type I and Type II alveolar cells after injury. 3.​ Alveolar macrophages (aka Dust cells) - Although not epithelial cells, these immune cells are found within the alveoli to phagocytose debris and pathogens. THE NASAL CAVITIES It comprises the: ★​ Respiratory epithelium ★​ Olfactory epithelium ★​ Paranasal sinuses REGIONS OF AIRWAY RESPIRATORY EPITHELIUM FUNCTIONS ​ Most of the nasal cavities and conducting portion of the system is lined with mucosa having ciliated ​ Bronchi - Repeated branching: conduct air deeper pseudostratified columnar epithelium and commonly into lungs known as respiratory epithelium ​ Bronchioles - Conduct air; important in bronchoconstriction and bronchodilation ​ This epithelium has five major cell types: Ciliated ​ Terminal bronchioles - Conduct air to respiratory columnar cells (the most abundant), Goblet cells (wi portions of lungs, exocrine club cells with several basal nuclei and apical domains filed w/ granules of protective and surfactant functions mucin glycoproteins). Brush coils, Small granule cells ​ Respiratory bronchioles - Conduct air deeper with (aka Kulchitsky cells) and Basal cells (mitotically some gas exchange, and protective and surfactant active stem and progenitor cells that gave rise to functions of club cells the other epithelial cell types) ​ Alveolar ducts and sacs - Conduct air, with much gas exchange ​ Alveoli - Sites of all gas exchange: surfactant from type ii pneumocytes: dust cells EPITHELIUM ​ Bronchi - Respiratory epithelium (aka pseudostratified columnar epithelium) ​ Bronchioles - Simple ciliated cuboidal to columnar, with exocrine club cells (aka Clara cells) ​ Terminal bronchioles - Simple cuboidal, ciliated cells and club cells (also contain chemosensory brush cells and DNES small granule cells aka Kulchitsky cells) 2 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED OLFACTORY EPITHELIUM ​ Vestibules of nasal cavities - Stratified squamous, keratinized (near the external nasal opening) to ​ A specialized region of the mucous membrane non-keratinized pseudostratified columnar covering the superior conchae at the roof of the epithelium (as it progresses inward) nasal cavity ​ Most areas of nasal cavities - Respiratory ​ It has three major cell types: Olfactory neurons, epithelium Supporting cells and Basal cells ​ Superior areas of nasal cavities - Olfactory, with bipolar neurons ​ The lamina propria of the olfactory epithelium possesses large serous glands, the olfactory glands THE PHARYNX (of Bowman), which produce a constant flow of fluid surrounding the olfactory cilia and facilitating the access of new odoriferous substances. ​ PHARYNX - The left and right nasal cavities open posteriorly into the nasopharynx, the first part of the pharynx ​ The nasopharynx is lined by respiratory mucosa which contains the medial pharyngeal tonsil as well as the openings of the two auditory tubes from each ​ The left and right nasal cavities each have two middle ear cavity components: the external, dilated vestibule and the ​ It is continuous caudally with the posterior part of internal nasal cavity. the oral cavity, the oropharynx (throat), the ​ Skin of the nose enters the nares (nostrils) partway mucosa of which has nonkeratinized stratified into the vestibule and includes sweat glands, squamous epithelium and includes the palatine and sebaceous glands, and coarse, moist vibrissae lingual tonsils (hairs), which filter out particulate material from ​ The oropharynx leads to a short, narrow region with Inspired air. similar lining, the laryngopharynx, continuous at its ​ Within the vestibule, the epithelium loses its inferior end with both the larynx and the esophagus keratinized nature and undergoes a transition to ​ Functions (pharynx) - air passage, food and liquid typical pseudostratified columnar epithelium which passage, swallowing (deglutition), voice resonance also lines the nasal cavities. (speech function) immune defense (pharynx houses the tonsils which play a role in trapping and PARANASAL SINUSES neutralizing pathogens entering through the mouth or nose) ​ are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull THE PHARYNX (FUNCTIONS) ​ They are lined with a thinner respiratory epithelium Summary: having fewer goblet cells. ​ Nasopharynx: conditions (warms, moistens and ​ The lamina propria contains only a few small glands filters) inhaled air and is continuous with the underlying periosteum. ​ Oropharynx protects against abrasion from food during deglutition ​ The paranasal sinuses communicate with the nasal ​ Laryngopharynx protects the mucosa from cavities through small openings: mucus produced mechanical damages caused by food and fluids there is moved into the nasal passages by the passing through activity of the ciliated epithelial cells. ​ Functions lightening the skull, resonance for voice, Air is moved through the lungs by a ventilating humidifying and warming air, mucus production, mechanism, consisting of the thoracic cage, intercostal shock absorption, immune defense muscles, diaphragm, and elastic components of the lung tissue. Take note: 3 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED ​ Function: Maintains an open airway (breathing and protecting the airway during swallowing), and sound production during phonation. ​ Also known as the voice box, because it houses the vocal cords THE PHARYNX (EPITHELIUM) Summary: ​ Nasopharynx: Pseudostratified ciliated columnar epithelium ​ Oropharynx: Non-keratinized stratified squamous epithelium ​ Laryngopharynx: Non-keratinized stratified squamous epithelium The Olfactory Epithelium Oropharynx & Laryngopharynx: Non-keratinized stratified squamous epithelium THE VOCAL CORDS/FOLDS OF THE LARYNX THE LARYNX ​ Each vocal fold is covered with nonkeratinized stratified squamous epithelium that protects the ​ The larynx is a short (4 cm x 4 cm) passage for air mucosa from abrasion and desiccation from rapid between the pharynx and the trachea air movement. ​ Its rigid wall is reinforced by hyaline cartilage (in the ​ A dense regular bundle of elastic connective tissue, thyroid, cricoid, and the inferior arytenoid the vocal ligament, supports the free edge of each cartilages) and smaller elastic cartilages (in the vocal fold epiglottis, cuneiform, corniculate, and the superior ​ Deep so the mucosa are large bundles of striated arytenoid cartilages), all of which are connected by fibers comprising the vocalis muscle that allow each ligaments vocal fold to be moved 4 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED ​ Functions, airway protection, facilitates breathing, speech and sound production VESTIBULAR FOLDS AND VOCAL CORDS ​ Below the epiglottis and vestibule of the larynx, the mucosa projects bilaterally into the lumen with two pairs of folds separated by a narrow space or ventricle. ​ The upper pair, the immovable vestibular folds, is partly covered with typical respiratory epithelium overlying numerous seromucous glands and occasional lymphoid nodules. ​ The lower pair of folds, the vocal folds (or cords), have features important for phonation or sound production: ​ During phonation muscles of the larynx draw the paired vocal folds together (adduction), which THE PLEURA narrows the opening between them, the rima glottidis, and ar expelled from the lungs causes the ​ The lung is the outer surface and the internal wall of adducted vocal folds (cords) to vibrate and produce the thoracic cavity is covered by a serous membrane sound called the pleura. THE LARYNX (EPITHELIUM) ​ The membrane lining the thoracic walls is the parietal pleura Take note: ​ Supraglottic region of the larynx (above the vocal ​ The membrane attached to lung tissue is called the cords) - has a stratified squamous epithelium, visceral pleura non-keratinized ​ The two layers are continuous at the hilum and are ​ Glottic region of the pharynx (vocal cords) - has both composed of simple squamous mesothelial stratified squamous epithelium, non-keratinized cells on a thin connective tissue layer containing ​ Subglottic region of the pharynx-has a collagen and elastic fibers. The elastic fibers of the pseudostratified ciliated columnar epithelium visceral pleura are continuous with those of the pulmonary parenchyma. EPIGLOTTIS ​ Between the parietal and visceral layers, the narrow ​ a flattened structure projecting from the upper rim pleural cavity is entirely lined with the mesothelial of the larynx, serves to prevent swallowed food or cells producing a thin film of serous fluid, which acts fluid from entering that passage. as a lubricant, facilitating the smooth sliding of one ​ Its upper or lingual surface has stratified squamous surface over the other during respiratory epithelium; at variable points on its laryngeal movements surface, this epithelium undergoes a transition to ciliated pseudostratified columnar (respiratory) THE PLEURA (EPITHELIUM) epithelium. Summary: ​ Mixed mucous and serous glands are found in the ​ Parietal pleura: Simple squamous epithelium lamina propria beneath the epithelium (mesothelium) 5 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED ​ Visceral pleura: Simple squamous epithelium (mesothelium) ​ Pleural Cavity: It is not lined by epithelium but is the potential space between the parietal and visceral pleura ​ Lung: The respiratory epithelium has pseudostratified ciliated columnar (upper airways-trachea and bronchi) while in the bronchioles, it has simple cuboidal epithelium, In the alveoli (for gas exchange), it has simple squamous. ​ Diaphragm: mesothelial (simple squamous), as it is a continuation of the pleura and peritoneum. Nasopharynx: Pseudostratified ciliated columnar epithelium THE TRACHEA The Vocal Cords/Folds ​ Trachea, also known as the windpipe, is a tubular structure that connects the larynx to the bronchi, providing passage for air to and from the lungs. ​ It measures 10-12 cm long in adults, is lined with typical respiratory mucosa in which the lamina propria contains numerous seromucous glands producing watery mucus. ​ It is supported by a series of 16-20 C-shaped hyaline cartilage rings to prevent collapse during inspiration ​ Its mucosa is lined with pseudostratified columnar epithelium with goblet cells that produce mucus to trap inhaled particles. ​ Functions: air conduction, filtration and protection, TYPE I ALVEOLAR CELLS/PNEUMOCYTES VS TYPE structural support ALVEOLAR CELLS/PNEUMOCYTES TYPE I TYPE II PNEUMOCYTES PNEUMOCYTES Shape Thin, squamous Cuboidal Surface 95% of alveolar 5% of alveolar Coverage surface surface Function Gas exchange Surfactant production, repair Division Non-dividing Can divide and differentiate 6 HISTOLOGY LABORATORY Term 2 SUMMARY/REVIEWER​ MED235 | A.Y 2024-2025 | PPT BASED Pseudostratified pseudostratified ciliated columnar 7