Histology 🔬 Flashcards
What is the respiratory system classified into?
There are 2 ways to classify respiratory system:
- Structural classification:
i. Upper respiratory tract
ii. Lower respiratory tract - Functional classification:
i. Conducting portion: For conduction and filtration of air.
ii. Respiratory portion: For Gas exchange (respiration).
What does the conducting portion of the respiratory system include?
1.Nasal cavities & sinuses.
2- Nasopharynx.
3- Larynx.
4- Trachea.
5- Bronchi.
6- Bronchioles.
7- Terminal bronchioles.
What does respiratory portion of the respiratory system include?
- Respiratory bronchioles.
- Alveolar ducts.
- Alveolar sacs.
- Alveoli.
What is the nose divided into?
1) The vestibule
2) 2 Nasal fossae separated into:
a. Respiratoryregion.
b. Olfactory region.
What is the vestibule and what is it lined by?
• It is the external dilated part.
• Lined by thin skin with thick hairs called vibrissae for filtration of air.
What is the respiratory region of the nasal fossa and what is it lined by?
➢ The constitutes the inferior 2/3 of the nasal fossae.
➢ It is lined by respiratory mucosa formed of: Epithelium and corium
What is a histological structure of the mucosa of the Respiratory region of the nasal Fossa?
Epithelium: Pseudostratified columnar ciliated epithelium with goblet cells.
Corium:
➢ Dense fibroelastic CT.
➢ Swell bodies: which are large venous plexuses
What is olfactory region of the nasal fossa?
➢ The constitutes the upper 1/3 of the nasal fossae (roof).
➢ It is lined by olfactory mucosa formed of : Epithelium and corium
What is the hosiological structure of the olfactory mucosa of the olfactory region of the nasal Fossa?
Epithelium: Neuroepithelium formed of 3 types of cells:
- Sustentacular (supporting) cells: Columnar cells
with oval nuclei and cytoplasm contains yellow pigments. Has apical microvilli. - Olfactory (sensory)cells: Bipolar nerve cells with oval nuclei. Their dendrites have long non motile cilia. Their axons collect to form the olfactory nerve. 3. Basal Cells: Small pyramidal cells responsible for regeneration.
Corium:
➢ Contains Bowman’s glands.
➢ These glands secrete serous fluid which acts as a solvent for the odorous gases.
What is the definition of paranasal sinuses?
Bilateral cavities in the ethmoid, frontal, maxillary, sphenoid bones of skull. Lined by thin respiratory epithelium with fewer goblet cells.
What is the definition of the nasopharynx and what lines it?
• It is the first part of the pharynx.
• Lined by respiratory epithelium
What is the histological structure of the nasopharynx?
Epithelium:
pseudo-stratified columnar ciliated epithelium with goblet cells.
Corium: contains Pharyngeal tonsils (adenoids).
What is the definition of Larynx?
The Larynx is a rigid short tube between the pharynx and trachea .
What is the histological structure of the Larynx?
Epithelium: Pseudo-stratified columnar ciliated with goblet Cells except vocal cords, anterior (lingual) surface of epiglottis.
Corium (Lamina propria): contains laryngeal cartilages (reinforces its wall).
from where does the epiglottis project and what is its function?
➢ It projects from the upper rim of larynx.
➢ It acts as a valve to prevent swallowed food or fluid from entering the trachea.
What is the histological structure of the epiglottis ?
Epithelium :
➢ The lingual surface: stratified squamous non keratinized epithelium.
➢ The laryngeal surface: pseudo-stratified columnar ciliated epithelium.
Lamina propria: contains glands.
What are the vocal cords?
They are 2 pairs of mucosal folds that extend into the lumen.
A. False vocal cords:
• The upper pair.
B. True vocal cords:
• The lower pair.
What is the function of the vocal cords?
The upper pair: • Protect larynx from foreign bodies.
The lower pair: • For phonation.
What lines the vocal cords?
The upper pair: • Lined by pseudostratified columnar ciliated epithelium.
The lower pair: • Lined by stratified squamous non keratinized epithelium.
What is the structure of the trachea?
formed of
1. Mucosa.
2. Submucosa.
3. Fibro-Cartilaginous coat.
4. Adventitia.
What is the structure of the mucosa of the trachea?
Epithelium: (7 types of cells)
1) Ciliated cells: columnar ciliated, cilia beat towards larynx.
2) Goblet cells: have expanded apical part distended with mucin granules.
3) Basal cells: stem cells
4) Brush cells: Columnar with few microvilli. Depleted goblet cells or intermediate between basal and goblet cells.
5) Kulchitsky cells: Have neuroendocrine function. Secretes serotonin & calcitonin.
6) Serous cells: Apical electron dense granules. Produce serous secretion.
7) Migratory cells.
Corium (Lamina Propria):
▪ Loose C.T rich in elastic fibers, blood vessels
▪ Elastic fibers condense to form elastic membrane between corium & submucosa.
What is the structure of submucosa of the trachea?
▪ Loose CT contains tracheal glands which:
▪ Mixed (mucus and serous).
▪ Open into the surface epithelium.
What is the structure of the fibrocartilaginous coat of the trachea?
- Dense CT contains 16-20 C-shaped rings of hyaline cartilage which are arranged above each other, maintain patency of the trachea and bridged at gaps between free edges by smooth muscle.
What is the structure of the adventitia of the trachea?
Dense CT contains blood vessels
What is the structure of extra pulmonary bronchi?
same structure as trachea
What is the structure of intrapulmonary bronchi?
- Mucosa:
Epithelium: pseudostratified columnar
ciliated with few goblet cells.
Corium: rich in elastic fibers.
- Muscle Layer: Spirally arranged smooth muscle fibers.
- Adventitia: Contains: Hyaline cartilaginous plates Mucous & serous glands. Lymphatic nodules.
Compare between trachea and intrapulmonary bronchus according to:-
Lumen
Wall
Mucosal folds
Epithelium
Elastic membranes
Submucosa
Glands
Cartilage
Muscle fibers
Lymphatic nodules
Lumen: wider - narrower
Wall: flattened posteriorly - circular
Epithelium: Pseudostratified columnar ciliated with goblet cells - Same but fewer goblet cells
Elastic membranes: Present in mucosa between the corium and the submucosa - No elastic membrane but elastic fibers are distributed between the cartilaginous plates in adventitia.
Submucosa: present - absent
Cartilage: C-shaped cartilaginous rings - Irregular numerous cartilage plates
Muscle fibers: Few, bridge the gap of C-shaped ring - Complete muscle layer surround the mucosa
Lymphatic nodules: absent - Lymphatic nodules in the adventitia
What is the diameter of bronchioles?
Less than 1 mm in diameter
What is the structure of bronchioles?
Structure: consists of
1. Mucosa
2. Muscle layer
3. Adventitia
“Same as intrapulmonary bronchus the mother”
What is the structure of mucosa of bronchioles?
Epithelium:
1) Ciliated cells: Simple columnar ciliated. “As they are narrow cells”
2) Non ciliated cells: (Clara cells)
o Columnar cells with rounded apex.
o Represent 50% of cells.
o Secretes surface active agent rich in lipoprotein
which prevents luminal adhesion.
“No goblet cells as the mucus of goblet cells will include the cells’
Corium: C.T rich in elastic fibers. “As intrapulmonary bronchus”
What is the structure of the muscle layer of bronchioles?
Well-developed “More than intrapulmonary Bronchus” spirally arranged smooth muscle fibers.
What is the structure of adventitia of bronchioles?
C.T which has
▪ No Cartilage
▪ No Glands
▪ No Lymphatic nodules
“No space”
What is the definition of terminal bronchioles?
- The smallest and terminal part of the conducting part.
What is the structure of terminal bronchioles?
- Cubical ciliated cells alternating with Clara cells “Even more than bronchioles” (50 % of lining cells).
What is the definition of respiratory bronchioles?
- Arise from the terminal bronchioles. 0.2-0.5 mm.
What are respiratory bronchioles lined By?
- Lined by cubical cells which are surrounded by CT contains elastic fibers & smooth muscle fibers.
What interrupts the walls of respiratory bronchioles?
- The wall is interrupted by alveoli which opens directly into the lumen.
What is the definition of alveolar ducts?
They are narrow tubes where the alveoli opens in their wall.
What is the definition of pulmonary alveoli and what is a group of alveoli what’s a common central space called?
- They are minute air spaces representing the functional and structural unit of the lung.
- Each group of alveoli which open into a common central space are called Alveolar sac.
What is the structure of pulmonary alveoli?
Structure:
- Alveolar epithelium.
Type 1 pneumocytes.
Type 2 pneumocytes - Interalveolar septum.
- Alveolar pores.
What is the number of type one pneumocytes?
- The majority of lining epithelium (95%).
What is the LM of type one pneumocytes?
- Flat squamous cells less than 0.2 um thickness with slightly thickened area containing nucleus. “For easy gas exchange”
What is the EM of type one pneumocytes?
➢ Attached to each other by occluding(tight) junctions
➢ Have thin basal lamina. “For easy exchange”
➢Perinuclear cytoplasm contains small Golgi, few
mitochondria and rER while cytoplasm of thin
portion is devoid of organelles.
What is the function of type one pneumocytes?
Provide very thin membrane through which Gas exchange occurs.
What is the number of type two pneumocytes?
5 % of lining epithelium
What is the LM of type two pneumocytes?
LM:
➢ Cuboidal cells with rounded central nuclei.
➢ Found at angles of interalveolar septa.
What is the EM of type two pneumocytes?
• Attached to type 1 by occluding (tight) junctions
• The cytoplasm contains many mitochondria, many rER,
prominent Golgi complex and electron dense lamellar
bodies rich in phospholipids.
What is the function of type two pnemocytes?
- Can divide so act as progenitor cells for type 1 and type 2 pneumocytes.
- Secrete pulmonary surfactant.
what is the definition and function of pulmonary surfactant?
• It is a mixture of phospholipids which lines the inner aspect of alveoli.
• It decreases surface tension so, prevent alveolar collapse.
What is the structure of intra-alveolar septum?
Formed of:
a. Alveolar epithelium on either sides.
b. Capillary network (pulmonary capillary bed).
c. Supporting network of reticular & elastic fibers and C.T.
cells ( Septal cells, mast cells, lymphocytes & WBC).
“No collagen fibers as their presents indicates fibrillation”
d. Basement membranes of alveolar epithelium & capillary beds.
- In certain sites, the 2 membranes fuse → alveolar capillary membrane. “To ease gas exchange”
What is the definition of blood air barrier?
It is the wall separating air in alveoli from blood in capillaries.
What is the structure of blood air barrier?
Formed of :
1. Type I alveolar cells.
2. The fused basal laminae of alveolar & endothelial
cells of capillaries.
3. The endothelial cells of capillaries.
What are alveolar pores (pores of kohn)?
▪ The interalveolar septa are interrupted by holes called alveolar pores.
▪ These pores are important for communication between the alveoli.
“As well as bacteria, that’s why these pores are few in the children”
What are alveolar macrophages?
mononuclear phagocytes of lungs which represent first line of defense.
What is the site of alveolar macrophages?
✓ Interalveolar septum.
✓ On luminal surface of alveoli.
What is the origin of alveolar macrophages?
blood monocytes.
What is the shape of alveolar macrophage cells and nuclei?
Shape: Branched cells with pseudopodia.
Nucleus: Irregular.
What is the shape of the cytoplasm of alveolar macrophages?
Vacuolated contains many lysosomes
What are the types of alveolar macrophages?
Dust cells and heart failure cells
What do dust cells and heart failure cells phagocytose respectively?
- Phagocytose dust or coal particles.
- Phagocytose extravasated RBCs.
Where or when or dust cells and heart failure cells found respectively?
- In smokers, cytoplasm is crowded with large irregular
heterogenous electron dense bodies. - In heart failure, cytoplasm contains many vacuoles with
hemosiderin granules.
What is the fate of alveolar macrophages?
Migrate to bronchi and carried by ciliary action through the upper airway to pharynx →swallowed or expelled in sputum .
What is the organizational structure of the kidney?
Medulla and cortex
What is the structure of the medulla of the kidney?
10-18 “many”medullary pyramids containing medullary rays (collecting tubules)
What is the structure of the cortex of the medulla?
Cortex cortices “cortex of the cortex” : under capsule
Cortex proper: around medullary rays “extend through the whole kidney”
Renal column of Bertini: between medullary pyramids
What is the histological structure of the kidney?
Stroma and parenchyma
What is the structure of the stroma of the kidney?
Capsule: fibrous C.T. with perirenal fat
Reticular tissue
“No trabecule”
What is the structure of parenchyma of the kidney?
Uriniferous tubule: (Nephron + Collecting tubule)
“Anatomical and physiological unit”
What is a nephron subdivided into?
1) Renal corpuscle
2) Proximal convoluted tubule (P.C.T.)
3) Loop of Henle.
4) Distal convoluted tubule (D.C.T.)
What is the diameter of renal corpuscle? (Malpighian corpuscle)
“The most active part”
range 50-250um “very small”
What forms the renal corpuscle?
o Bowman’s capsule “cover the glomerulus”
o Glomerulus
What is the definition of Bowmans capsule?
Double walled cup shaped capsule
What forms Bowmans capsule?
Two layers:
Outer parietal layer (capsular epithelium) : simple squamous epithelium
Inner visceral layer (Glomerular epithelium) : podocytes
What is the definition of podocytes?
Large flattened modified epithelial cells.
What are the parts of podocytes?
major and minor processes with filtration slits.
What is the function of podocytes?
synthesis of glomerular basement membrane.
What is the definition of the glomerulus?
Is a tuft “group” of capillary loops
From where does the glomerulus arise?
afferent arteriole at the vascular pole (non-filtered blo
Where does the glomerulus drain into?
efferent arteriole (filtered blood)
What is the E.M of the glomerulus?
o Fenestrated endothelium (open) “for filtration”
o Basement membrane (continuous thick)
What is the definition of mesangial cells?
Between glomerular capillaries
What is the shape of mesangial cells?
Stellate shape with basophilic “RER” cytoplasm
What is the function of mesangial cells?
o Continuous turnover of basement membrane
o Phagocytosis
o Supportive: secrete collagen
What is the definition of blood renal barrier (filtration barrier0?
It is a barrier that separates blood in glomerular capillaries from capsular space in Bowman’s capsule
“In between the 2 layers”.
What is the function of blood renal barrier?
blood plasma dialysis
What are the parts of blood arena barrier and what is the function of each part?
o Glomerular endothelium: holds blood cells
o Basement membrane: holds plasma ptn albumin
o Filtration slit diaphragm: holds large molecule
What does history of severe pain in the side and the back and spreading to the lower abdomen and history of bloody urine and fever indicate?
- the case with renal calculi (kidney stones) found in renal pelvis.
Why do kidney stones cause pain?
- Movement of the stone caused severe pain and bloody urine.
How could kidney stones be corrected?
- It can be corrected by either surgical removal or breaking by shock waves
What is a Continous and thick basement membrane of the glomerulus formed from?
made of fusion of two membranes (one of the visceral layer, and the other of the capillary). It is about 100 nm.
What are the layers of the basement membrane of the glomerulus?
• It shows three layers:
Lamina densa (central and dark).
Lamina Lucida externa (outer and pale).
Lamina Lucida interna (inner and pale)
What is the extent of PCT?
o Arise from urinary pole of renal corpuscle
o Continuous with the descending loop of Henle (in the medullary pyramid)
“Urinary pole to des. Loop of henle”
What is the function of PCT?
“Higher work that DCT”
o Reabsorption of water and sodium
o Reabsorption of glucose, plasma proteins and amino
acids
o Excretion of some metabolites (as dyes)
“Literally everything”
What is the definition of the DCT?
o Starts as continuity of ascending loop of Henle
o Ends in a collecting tubule
“Asc. Loop of henle to collecting tubules”
What is the function of DCT?
o Reabsorption of water and sodium (under control of antidiuretic hormone)
o Reabsorption of sodium (under the control of aldosterone hormone
“Less than PCT, Under the effect of hormones”
Na, water —-> ADH
Na —-> aldosterone
Compare between PCT and DCT Acc to:-
Number
Shape
Nucleus
Side border
Luminal border
Base of cell
Cytoplasm
Number: 3-5 cells “as they are big” - 5-8 cells
Shape: cubical - less cubical
Nucleus: basal & rounded - central & rounded
Side border: not clear - clear
Luminal border: microvilli (brush appearance) - microvilli (few & short) “as if it pushes urine”
Base of cell: basal mitochondrial striations - fewer basal mitochondrial striations
Cytoplasm: deep acidophilus and granular “due to mitochondria” - pale acidophilic and non granular
What is the definition of loop of Henle?
o U shaped tube
o Connecting P.C.T. & D.C.T.
What is the function of the loop of Henle?
o Keeping the tissue fluid in the medullary pyramids “outside loop of henle” hypertonic “have higher osmotic pressure” by excretion of NaCl into it.
o Allowing water to pass from C.T. to it thus making the urine hypertonic
“The urine becomes the one that is hypertonic in the end”
What is the histological structure of loop of Henle?
o Descending limb:
▪ Thick part lined by simple cubical epithelium.
▪ Thin part lined by simple squamous epithelium.
o Ascending limb:
▪ Thin part lined by simple squamous epithelium.
▪ Thick part lined by simple cubical epithelium.
How are ducts of Bellini formed?
- In cortex: Each C.T drains 5-10 nephrons.
- In medulla: 6-8 C.T. open into large duct (of Bellini) that opens into medullary pyramid
What is the function of collecting tubules?
o Conduction of urine
o Water reabsorption from urine
“Like PCT & DCT”
What is a histological structure of collecting tubules and duct of bellini?
o Collecting tubule: lined by cubical cells with clear basophilic cytoplasm “like PCT & DCT but basophilic”
o Duct of bellini: lined by columnar “As they are bigger that C.T” cells with clear basophilic cytoplasm
What is the definition of juxtaglomerular complex?
- It Is a secretory complex “renin and erythropoietin” at the vascular pole of the renal corpuscle.
What is juxtaglomerular complex formed of?
o Macula densa cells: modified cells lining part of D.C.T. “In DCT”
o Juxtaglomerular cells: modified smooth muscle cells “in afferent”
o Lacis cells (polar cushion): small cubical supporting
What is the function of juxtaglomerular complex?
o Regulation of blood pressure: as J.G. cells secrete renin hormone
o Secrete erythropoietin factor: stimulates erythrocytes development in bone marrow
What is a histological structure of urinary bladder?
“Like bronchi”
1) Mucosa:
• Transitional “specific” epithelium
• Corium
2) Muscle layer: “for expulsion of urine”
• Inner longitudinal
• Middle circular
• Outer longitudinal
3) Adventitia: serosa in the fundus
What is a histological structure of ureter?
Same as urinary bladder but Muscle layer formed of:
- Upper 2/3: inner longitudinal and outer circular
- Lower 1/3: as urinary bladder (3 layers)
“No middle, so the outer becomes circular”
What is te length and diameter of PCT?
• Length: 15mm
• Diameter: 60um
What is the length and diameter of DCT?
• Length: 5mm
• Diameter: 30-50 um
