Histology of the Respiratory System PDF

Histology 1st year students Lec.3: Histology of Respiratory System Dr. Samer khalid ali BSc. Pharm., MSc. Pharmaceutics PhD in pharmaceutics  Respiratory System  Respiratory System consist of:- 1. Conducting Part; responsi...

Histology 1st year students Lec.3: Histology of Respiratory System Dr. Samer khalid ali BSc. Pharm., MSc. Pharmaceutics PhD in pharmaceutics  Respiratory System  Respiratory System consist of:- 1. Conducting Part; responsible for passage of air and conditioning of the inspired air. Examples: nasal cavities, pharynx, trachea, bronchi and their intrapulmonary continuations. 2. Respiratory Part; involved with the exchange of Oxygen and Carbone dioxide between blood and inspires air, includes the lungs  General Anatomy of The Respiratory Sys. 1. Consists of a tube that divides into small branching tubes in the lungs: external nares →nasal cavity → nasopharynx → laryngopharynx → larynx → trachea → primary bronchi → lungs (secondary bronchi → tertiary bronchi → bronchioles → alveolar sacs → alveoli). 2. The histology along the respiratory tract changes from the trachea to the tertiary bronchi, Tracheal tract is lined with ciliated pseudo-stratified columnar epithelium, smooth muscle and cartilage rings. Bronchioles are lined with cuboidal epithelium Alveolar ducts to the alveoli, the tract is lined with simple squamous epithelium. 3. The left lung contains 2 lobes – superior and inferior lobes, while the right lung contains 3 lobes – superior, middle, and inferior lobes. Each lobe is highly vascularized and contains part of the bronchial tree. 4. Lower to the lungs is a sheet of skeletal muscle under involuntary control, called diaphragm, to facilitate the control of thoracic volume.  Anatomy of Respiratory Organ 1. Nose and nasal cavity:  Gases in the environment enter the respiratory tract through two openings called external nares which contain hairs to prevent dust particles to come in.  The space within the nose, called nasal cavity, is lined with ciliated pseudostratified columnar epithelium to provide a defense mechanism where cilia and mucus (from goblet cells) expel foreign substances.  2. Larynx (voice box):  The larynx is a rigid, short passage for air between the pharynx and the trachea. Its wall is reinforced by hyaline cartilage and smaller elastic cartilages, all connected by ligaments.  Elastic tissues in the larynx also allow different sounds to be generated when air flow passes through the larynx.  Located beneath the nasal pharynx and laryngo-pharynx, a cartilage at the top called epiglottis remains upright when gases are entering or exiting the trachea, through an opening called glottis.  3. Trachea:  Long, straight tube beginning from the larynx to the lungs.  Cilia on its inner wall lining always, expel foreign substances trapped in mucus back to the naso- pharynx and oropharynx.  Trachea is open because of support by 20 C-shaped cartilage rings, so that gases can pass freely.  Histology of Trachea Mucosa; -Epithelium -Lamina propria Sub mucosa Cartilage &muscle layer Adventitia  Histology of Trachea 1- Mucosa Epithelium -Pseudo stratified ciliated columnar -Type of Cells; Cell - Ciliated columnar cells - Goblet cells - Brush cells - Basal cells -Granule (kulchitsky) cells Secretory cell -Clara cells (bronchiolar cells) surfactant secretion Lamina propria - loose connective tissue and elastic fiber Lymphocyte, Mast cells, Blood vessels  Histology of Trachea 2-Submucosa Loose connective tissue Tracheal glands- mixed (serous &mucus) glands Blood vessels and ducts 3- Cartilage &smooth muscle layer ”C” Shaped hyaline cartilage having perichondrium and chondrocytes Ends of cartilage connected by smooth muscles 4-Adventitia- fibro elastic tissue