RESPIRATORY SYSTEM

(I)Conducting portion (Mention……) (II) Respiratory portion ( “ …….)

NASAL CAVITY (N.C.) (1)Vestibule. (2)Nasal Fossae (posterior portion of N.C.): a- Olfactory portion. b- Respiratory portion. Nasal septum divides the nasal cavity into two halves.

VESTIBULE OF NASAL CAVITY Lining: is lined with skin. 1- Epidermis ( Keratinized stratified Squamous epithelium). 2- Dermis. 3- Vibrissae. 4- Sebaceous glands. 5- Sweat glands. Wall:

RESPIRATORY AREA OF NASAL CAVITY (RESP. PORTION OF NASAL FOSSA) (A)Epithelium: Pseudo-stratified ciliated columnar epithelium with goblet cells (Respiratory epithelium). (B) Lamina propria (Corium): 1- C.T.: richly (highly) vascularized. 2- Large arterial plexuses & venous sinuses (Highly vascular),especially in region of conchae & anterior part of nasal septum. 3- Many seromucous glands (acini). 4- Abundant lymphoid elements: Including lymphoid nodules, plasma cells & mast cells.

RESPIRATORY EPITHELIUM L/M: Pseudo-stratified columnar ciliated epithelium with goblet cells. E/M: 6 cell types ( all touch the basement m) 1- Ciliated columnar cells: 30% 2- Goblet cells: 30% 3- Basal cells: are stem cells (30%) 4- Brush cells (small granule mucous cells): (3%) are sensory receptors or degranulated goblet cells. 5- DNES cells (small granule cells) (K cells) : 3-4% are neuroendocrine cells 6- Serous cells: 3%

RESPIRATORY MUCOSA OF NASAL CAVITY

RESPIATORY EPITHELIUM

PARANASAL SINUSES Lining: 1- Respiratory epith. (Mention…….) 2- Lamina propria. CLINICAL APPLICATION: Sinusitis.

MEDICAL APPLICATION IMMOTILE CILIA SYNDROME: C.P.: 1- Chronic respiratory tract infection ( M & F) 2- Infertility in males (M). Etiology: Immobility of cilia & flagella (induced by deficiency of dynein protein)

MEDICAL APPLICATION Smoking & resp. epith.: 1- ↑ Goblet cells → ↑ Mucus 2- ↓ Ciliated cells ( due to CO ): → ↓ Movement of the mucus layer. 3- Metaplasia: Transformation of resp. epith. into str.squamous epith.(non-keratinized). 4- Squamous cell carcinoma.

MEDICAL APPLICATION Allergic reactions & inflammation → Abnormal engorgement of swell bodies ( large arterial plexuses & venous sinuses in lamina propria over the conchae) → Restrict air flow.

OLFACTORY MUCOSA

OLFACTORY AREA OF NASAL CAVITY OLFACTORY MUCOSA Site: 1-Roof of nasal cavity. 2-Upper part of nasal septum. 3-over superior concha. Structure: (A)Olfactory epithelium: Pseudo-stratified columnar epith. 1- Supporting (sustentacular) cells 2- Olfactory cells (olfactory nerve cells) 1 & 2 are connected together by junctional complexes. 3- Basal cells. (B) Lamina propria: contains: 1- Highly (richly) vascularized loose to dense C.T. 2- Bowman’s glands (serous acini). 3- Axons of olfactory nerve cells + Schwann cells. 4- Rich vascular plexus. 5- Numerous lymphoid elements.

OLFACTORY EPITHELIUM 1- Sustentacular (supporting) cells: Columnar cells with: Apical striated border (microvilli). Oval Nucleus. Apical cytoplasm has secretory granules with yellow pigments. Junctional complexes with olf. Vesicles. Function: Physical support, nourishment & electrical insulation for olfactory cells.

OLFACTORY EPITHELIUM 2- Olfactory cells: Are bipolar neurons Dendrite has olfactory vesicle. Olfactory vesicle has 6-8 olfactory cilia. Olfactory cilia are nonmotile Microtubules of olfactory cilia: (9x2+2x1 then 9x1+2x1). Cell body with spherical nucleus. Axons are unmyelinated with Schwann cells. Axons will collect to form the olfactory nerve.

OLFACTORY EPITHELIUM 3- Basal cells: Short basophilic pyramidal cells. Function: Replacement of sustentacular & olfactory cells.

OLFACTORY MUCOSA

LARYNX (A)Mucous membrane: 1- Epithelium: (2 types: a- respiratory epith. b- non-keratinized str.sq. epith.----Where?) 2- Lamina propria (contents: ) There are 2 pairs of shelf-like mucosal folds: 1- Vestibular folds: Are immovable. L/M: a- Resp. epith. b- Lamina propria: Loose C.T. with seromucous glands lymphoid elements & adipose cells. 2- VOCAL FOLDS (CORDS): have: a- Vocal ligament: bundles of parallel elastic fibers (dense regular elastic C.T.). b- Vocalis muscle: Skeletal muscle.

(B) Cartilages: 1- Hyaline cartilages: Thyroid, Cricoid, Body of arytenoids. 2- Elastic cartilages: Epiglottis, Corniculate, Cuneiform, Tips of arytenoids. (C) Extrinsic and intrinsic muscles: all are skeletal. (D) Ligaments.

LARYNX

Thyroid cartilage Glands

LARYNX Vocal fold Respiratory epith. Bundles of skeletal muscle fibers

LARYNX

VOCAL FOLD (CORD)

TRACHEA The wall of trachea is formed of: (1)Mucosa. (2)Submucosa. (3)Adventitia.

MUCOSA OF TRACHEA (1)Epithelium: Respiratory epithelium (2)Lamina propria: Loose, fibroelastic C.T. containing: a- Lymphoid elements (e.g. lymphoid nodules & lymphocytes). b- Mucous & seromucous glands. (3) Elastic lamina: Dense layer (thick bundle) of elastic fibers. It separates lamina propria from submucosa. N.B. Mucosa is non-folded except posteriorly.

SUBMUCOSA OF TRACHEA Contents: 1- Dense irregular fibroelastic C.T. (others:loose) 2- Numerous mucous & seromucous glands. 3- Lymphoid elements. 4- Rich blood & lymph supply. N.B. Other textbooks reported that submucosa of trachea is loose C.T.

ADVENTITIA OF TRACHEA Contents: 1- Fibroelastic C.T. 2- C-shaped rings (12-16) of hyaline cartilage. Trachealis muscle (bundle of SMF) bridges (connects) the open ends of each C-shaped ring of cartilage. Perichondrium of C-shaped rings of hyaline cartilage are connected together by dense fibroelastic CT.

TRACHEA

EXTRAPULMONARY BRONCHUS (1ry BRONCHUS) Generally have the same histological appearance as the trachea.

BRONCHUS

INTRAPULMONARY BRONCHUS

INTRAPULMONARY BRONCHUS 2ry & 3ry BRONCHI) 1- Mucosa. 2- Muscle coat. 3- Submucosa. 4- Adventitia.

INTRAPULMONARY BRONCHUS (1)Mucosa: It has longitudinal mucosal folds. a- Epithelium: Respiratory epith. b- L.P.: Fibroelastic C.T. (loose C.T. rich in elastic fibers). It contains seromucous glands. “ “ lymphoid elements. N.B. No elastic lamina.

INTRAPULMONARY BRONCHUS (2) Muscle coat (complete): Two distinct layers of SMF spirally arranged in opposite direction (crisscrossing bundles of spirally arranged SMF).

INTRAPULMONARY BRONCHUS (3) Submucosa: It contains: a- Seromucous glands. b- Lymphoid elements.

INTRAPULMONARY BRONCHUS (4) Adventitia: Contents: a- Loose C.T.: Contains radially arranged elastic fibers to connect with counterparts of neighbouring bronchial tree. b- Irregular plates of hyaline cartilage (complete layer). c- Solitary lymphoid nodules. d- Seromucous glands.

INTRAPULMONARY BRONCHUS 2ry Bronchi (lobar bronchi): 3+2 3ry Bronchi (segmental bronchi): 10+10

BRONCHIOLES 1- Preterminal ( 1ry ) Bronchioles (Bronchioles). 2- Terminal ( 2ry ) Bronchioles. 3- Respiratory ( 3ry ) Bronchioles.

PRETERMINAL BRONCHIOLES Are 1mm or less in diameter. Each bronchiole supplies pulmonary lobule.

Preterminal Bronchioles (1) Mucosa: has longitudinal folds: (A) Epithelium: S. col. ciliated Epith. with occasional goblet cells only in the initial segments. Then, s. cuboidal partially ciliated with occasional Clara cells (in smaller pret. Br.) (B) Lamina propria: C.T. (rich in elastic fibers) (2) Smooth muscle: hellicaly arranged SM layers. (3) Adventitia: loose fibroelastic C.T. N.B. No cartilage, No glands, No lymphoid nodules.

Terminal Bronchioles Similar structure, but: Epithelium: Simple cuboidal partially ciliated epithelium With Clara cells. Are less than 0.5mm in diameter. Each supplies lung acinus.

BRONCHIOLE

TERMINAL BRONCHIOLE

Respiratory Bronchioles Similar structure to terminal bronchioles But their walls is interrupted by the presence of few pulmonary alveoli.

RESPIRATORY BRONCHIOLE

RESP. BRONCGIOLE & ALVEOLUS

RESP. BRONCHIOLE & ALV. DUCT

TERMINAL & RESPIRATORY BRONCHIOLES

Clara cells

CLARA CELLS Structure: columnar cells (non ciliated). Dome-shaped apices with microvilli. Numerous apical secretory granules (of glycoproteins). Abundant rER.

CLARA CELLS Function: 1- Protect the bronchiolar epith. By their secretion. 2- Degrade toxins in inhaled air by cytochrome p-450 enzymes (produced by sER) 3- Divide to regenerate the bronchiolar epith 4- May produce surfactant-like material.

ALVEOLAR DUCTS The wall of alveolar duct consists almost of pulmonary alveoli. (1)Lining Epith.: Squamous alveolar cells ( Type I Pneumocytes ) (2) Lamina propria: a- Elastic & Reticular fibers. b- Smooth muscle cell surrounds the opening of alveolus (small muscle knob). N.B. Alveolar duct → ends by: atrium → communicates with: 2-3 alveolar sacs

PULMONARY ALVEOLI Definition: They are small outpouchings of respiratory bronchioles, alveolar ducts & alveolar sacs.

PULMONARY ALVEOLI *Interalveolar septa. *Blood-air barrier ( Blood-gas barrier) *Alveolar epithelium. *Lung macrophages (alveolar macrophages) *Alveolar pores.

INTERALVEOLAR SEPTA (A)Alveolar Epithelium: (B) Interstitium

Blood-air barrier

ALVEOLAR EPITHELIUM (1)Type I Pneumocytes (Type I alveolar cells) (Squamous alveolar cells). (2) Type II Pneumocytes (Type II alveolar cells) ( Septal cells) ( Great alveolar cells)

ALVEOLAR EPITHELIUM (1)Type I Pneumocytes: - line 95% of the alveolar surface. - L/M: simple squamous epith., highly attenuated cells. - E/M: Abundant pinocytotic vesicles, Are connected together and with type II cells by occluding junctions. -Functions: 1- Exchange of gases. 2- may play role in surfactant turnover.

Type II Pneumocytes(septal alveolar cells): -Line 5% of the alveolar surfaces. - Are more numerous than type I pneumocytes. -L/M: Are cuboidal cells ( other textbooks: rounded cells). Usually found in groups of 2-3 cells. Usually found at sites of union of septa. Foamy or vesicular cytoplasm. Nucleus: central, rounded, vesicular. -E/M: connected with type I cells by occluding junctions Dome-shaped apical surface. Short apical microvilli. Abundant mitochondria, RER, Well-developed Golgi. Membrane-bound Lamellar bodies (contain concentric or parallel lamellae limited by a unit membrane) (contain surfactant).

-Renewal: By mitotic cell division ( Type II cells can divide to replace: 1- Their own population 2- Type I cells). -Function: 1- Synthesis & secretion of pulmonary surfactant ( phospholipids+GAGs+Pr.): a- lower ( ↓ ) alveolar surface tension→ reduce effort to inflate pulm. Alveoli. b- Phagocytosis of pulmonary surfactant. b- has bactericidal effect. 2-Renewal of alveolar epithelial cells.

Type II Pneumocyte (E/M)

Type II Pneumocytes

ALVEOLAR EPITHELIUM

Interstitium of interalveolar septa (1)Pulmonary Capillaries: -The richest capillary network in the body - Continuous blood capillaries - Endothelium shows numerous pinocytotic vesicles. (2) Interstitial C.T.: a- C.T. Fibers: elastic & reticular. b- C.T. Cells: Fibroblasts, Macrophages, Mast cells, Leucocytes.

BLOOD-GAS BARRIER Definition: It is the region of the interalveolar septum that is traversed by O2 and CO2

BLOOD-GAS BARRIER BLOOD-AIR BARRIER Components: 1- Thin layer of surfactant. 2- Type I pneumocyte. 2- Fused basal laminae of type I pneumocytes & endothelial cells of the pulmonary capillary. 3- Endothelial cells of the pulmonary capillary. Thickness: µm.

CLINICAL APPLICATION Respiratory Distress Syndrome Etiology: Deficiency of surfactant in premature infants → Pulmonary alveoli are collapsed ( They failed to inflate). Treatment: Administration of glucocorticoids→ Induces synthesis of surfactant.

Alveolar Macrophages (Dust Cells) Sites: (1)In lumen of pulmonary alveoli. (2)In pulmonary interstitium.

ALVEOLAR PORES Diameter: 8-60 µm. Function: Equalize air pressure in the alveoli.

CLINICAL APPLICATION Emphysema Etiology: Major cause is: smoking → Destruction of interalveolar septa → Enlargement of pulmonary alveoli → Respiratory insufficiency.

PLEURA (1)Parietal pleura. (2)Visceral pleura. L/M: 1- Simple squamous mesothelial cells. 2- Lamina propria: Fine C.T. layer that contains collagen & elastic fibers.