Histology Short Question And Answers

Question 1. Histology of cartilage
Answer:

Cartilage is a modified connective tissue

• Histology of cartilage It consists of
  1. Cartilage cells called chondrocytes
     • They are widely separated
     • They lie in spaces called lacunae
     • Initially
       • Cells are small & active
       • Nucleus is euchromatic

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• 1. • • Consists of prominent cell organelles
     • Later
       • Cell enlarges & becomes inactive
       • Nucleus is heterochromatic
       • Cell organelles are less prominent
  2. Matrix
     • It consists of homogeneous ground substance within which fibres are embedded
       1. Ground substance
          • It consists of complex molecules containing proteins & carbohydrates
          • These molecules form a meshwork filled with water & dissolved salts
       2. Fibres
          • Mainly it consists of Collagen fibres
          • Composed of Type II collagen

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Cartilage Types:

Depending on the number & type of fibres present in matrix, cartilage is classified into:

1. Histology of cartilage Hyaline cartilage

• Contains Collagen fibres

2. Histology of cartilage Fibrocartilage

• Contains dense fibrous tissue

3. Histology of cartilage Elastic cartilage

• Contains numerous elastic fibres

Question 2. Histology of Hyaline Cartilage
Answer:

• It is transparent so called hyaline cartilage
• Histology of hyaline cartilage It consists of
  1. Intercellular substance
     • It appears homogeneous
  2. Matrix
     • Towards center
       • Chondrocytes are large & present in groups
       • These groups are called cell nests
       • Matrix is stained deeply around individual cells & around cell nests
       • Here it is called territorial matrix
       • The rest of the matrix is called interstitial matrix
     • Towards periphery
       • Chondrocytes are small
       • They are arranged parallel to the surface
  3. Ground substance
     • It resists compressive forces
     • It consists of numerous Collagen fibres
     • These fibres resist tensional forces

Histology of hyaline cartilage Distribution:

• Costal cartilage
• Articular cartilage
• Skeletal framework of larynx
• Walls of trachea & large bronchi
• Parts of nasal septum
• Epiphysis connected to diaphysis

Question 3. Histology of Bone
Answer:

• It is a modified connective tissue
• It consists of Bone cells
• Histology of bone They are:
  1. Osteocytes
     • They are widely separated by Intercellular substance
     • This Intercellular substance consists of ground substance composed of Collagen fibres & mineral salts
     • They lie in lacunae
     • Contains eosinophilic cytoplasm
     • It decreases with age
       Functions:
     • Maintain the integrity of the lacunae & canaliculi
     • Help in removal or deposition of matrix & calcium
  2. Osteoblasts
     • These are bone forming cells
     • They are present lining growing surfaces of bone
     • There are numerous gaps between adjacent cells
     • Nucleus is ovoid & euchromatic
     • Cytoplasm is basophilic
       Functions:
     • Lay down organic matrix of bone
     • Responsible for calcification of the matrix
     • Help to shed off matrix vesicles
     • Inhibit or stimulate Osteoclasts
  3. Osteoclasts
     • They are bone resorbing cells
     • They are present over the resorptive surface of bone
     • They occupy bays called lacunae of Howship
     • They have numerous nuclei
     • They are derived from monocytes of blood
  4. Osteoprogenitor cells
     • They are precursor of osteoblasts & osteoclasts
     • They resembles fibroblasts in appearance
     • In fetus it is present at the site of bone formation
     • In adults present over bone surfaces
  5. Bone lining cells
     • They form a continuous epithelium like layer on bony surfaces They are flattened cells
     • They are present on both periosteal & endosteal surfaces

Histology of bone Classification:

1.

1. Lamellar bone
2. Woven bone

2.

1. Compact bone
2. Cancellous bone

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Question 4. Histology of Skeletal Muscle
Answer:

• The muscle present in relation to bony skeleton is called skeletal muscle
• Histology of skeletal muscle It is made up of

1. 1. Muscle fibres
      • They are long & cylindrical
      • They are arranged in bundles called fasciculi
      • Each muscle fibre is covered by a plasma membrane called sarcolemma
      • They contain:
        1. Nucleus
           • Elongated nucleus arranged along periphery
        2. Cytoplasm
           • It is called sarcoplasm
           • It contains usual cell organelles present near the nucleus
           • It also contains myofibrils
           • These fibrils are arranged in groups called the fields of Conheim
           • Between the myofibrils there is presence of membrane lined tubes called sarcoplasmic reticulum
           • Size of fibres:
             • Length30 cm
             • Diameter 10 to 60 micrometer
2. Skeletal Muscle Connective tissue
   • It supports & unites muscle fibres
   • The connective tissue surrounding individual muscle fibre is called endomysium
   • The connective tissue surrounding individual fasciculi is called perimysium
   • Finally the connective tissue surrounding the entire muscle is called the epimysium
     Striations:
   • The skeletal muscle shows prominent transverse striations
   • These striations on staining shows alternate dark & light bands
     1. A band
        • It is dark band
     2. I band
        • Light band of muscle
     3. Z band
        • It is a thin dark line present between I band
     4. H band
        • It is lighter band present between A band
     5. M Band
        • Thin dark line present in center of H band
        • The part present between two consecutive Z bands is called Sarcomere.

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Question 5. Histology of Medium Sized Artery
Answer:

• The blood vessels that take blood from heart to various tissues are called arteries
• The wall of medium sized artery is made up of:
  1. Tunica intima
     • It is innermost layer
     • Fibres in this layer runs longitudinally
     • Histology of medium sized artery It consists of:
       1. An endothelial lining
          • It is smooth lining which is sensitive to alterations in blood pressure
       2. Basal lamina
          • It is thin layer of glycoprotein lining external portion of endothelium
       3. Delicate layer of endothelial connective tissue
          Internal elastic lamina
       4. It is a membrane formed by elastic fibres
  2. Tunica media
     • It is middle layer
     • It consists of elastic tissue or smooth muscle
     • It may also contain some connective tissue
     • Fibres in this layer are circularly arranged
     • On outside of this layer, a membrane is formed of elastic fibres called external elastic lamina
  3. Tunica adventitia
     • It is outermost layer
     • It consists of connective tissue with predominate collagen fibres
     • These fibres are arranged longitudinally
     • This layer prevents undue stretching or distension of artery

Question 6. Histology of Lymph Node
Answer:

• They are small beanshaped structures scattered along the course of lymphatic vessels
• Its concavity constitute a hilum for entry & exit of blood vessels
• Histology of medium sized artery It consists of:
  1. Connective tissue framework
     • Interstitial spaces of it is filled with lymphocytes & other cells
     • Lymph node is surrounded by a capsule
     • It consists of mainly collagen fibres & some elastic fibres & smooth muscle
     • Remaining part of lymph node contains reticular fibres
     • Each lymph node is divided into lobules by septa or trabeculae that extendsfrom capsule into the node
  2. Cells
     1. Lymphocytes
        • Lymphocytes present in blood are of two types
          1. BLymphocytes
             • It divides rapidly
             • Matures into plasma cells
             • Functions:
             • Remain in lymph node as memory cells & produce plasma cells
             • Return to blood stream via lymph
             • Concern with humoral immunity
          2. T-Lymphocytes
             • Present in between the lymphatic nodules
             • Concern with cellmediated immunity
     2. Fibroblasts
        • Spindle shaped cell
        • Present along reticular fibres
     3. Macrophages
        • Present in lymph sinuses & around germinal center
        • More in medulla than in cortex
        • Help in phagocytosis
     4. Endothelial cells
        • Present lining the blood vessels of lymph node
     5. Pericytes & smooth muscle cells
        • Present around the blood vessels

Histology of medium sized artery Zones:

1. Cortex
   • Outermost zone
   • Contains densely packed lymphocytes
   • It is darkly stained
   • Several rounded areas called lymphatic follicles or nodules are present
   • Each nodule contains a germinal center surrounded by densely packed lymphocytes
2. Medulla
   • It is lighter zone surrounding cortex
   • Contains fewer lymphocytes
   • These lymphocytes are arranged in the form of branching

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2. Histology of medium sized artery Lymphocytes

• Present in the cortex of each lobules as densely packed
• Less densely packed in medulla of lobule

3. Histology of medium sized artery Macrophages

• Placed subjacent to the capsule at corticomedullary junction & in the medulla
  Functions:
• Phagocytosis
• Deeper cells are dendritic

4. Histology of medium sized artery Corpuscles of Hassall

• They are small rounded cells
• Present in medulla

Question 7. Histology of Lung
Answer:

• The lung is divided into numerous lobules
• These lobules are obtained by following branching

Histology of lung Branching:

• Principal bronchus divides into secondary or lobar bronchi
• Each lobar bronchi divides into tertiary or segmental bronchi
• Each segmental bronchi divides into smaller bronchi that end in bronchioles

Histology of lung Changes seen in subsequent branching:

• Cartilage becomes irregular
• Amount of muscle increases
• Subepithelial lymphoid tissue increases
• Epithelial changes occur from pseudostratified to cuboidal epithelium

Histology of lung Structure of lung:

• The lung is divided into numerous lobules
• These lobules receives lobular bronchiole
• Lobular bronchiole divides into terminal bronchiole
• Each terminal bronchiole ends into respiratory bronchiole Each respiratory bronchiole ends into alveolar ducts
• Each alveolar duct ends into atrium which leads to alveolar sacs
• Each alveolar sac contains alveoli

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Question 8. Histology of Parotid Gland
Answer:

• In the parotid gland the spherical secretory end peices are all serous
• The pyramidal shaped acinar cells have a spherical, basally situated nucleus
• It surrounds a small, central lumen
• It may contain fat cell spaces

Histology of parotid gland Ducts:

1. Intercalated ducts

• They are numerous & long
• They are lined with cuboidal epithelium
• Nuclei of myoepithelial cells may appear

2. Striated ducts

• They are numerous
• They are round or elongated tubules
• It consists of simple columnar epithelium
• Nuclei are round & centrally placed
• Lumina are relatively larger in size

Question 9. Histology of Esophagus
Answer:

• Oesophagus is a tube
• Histology of esophagus It has four layers
  1. Mucosa
     • It shows several longitudinal folds that disappear when the tube is distended It is lined by stratified Squamous epithelium
     • Finger like processes project from connective tissue into the epithelium
     • This prevents separation of epithelium
     • Lamina propria contains some mucous glands
     • The muscularis mucosae is absent or poorly developed
  2. Submucosa
     • It contains compound tubuloalveolar mucous glands
     • These glands are present at the level of bifurcation of the trachea
  3. Muscle layer
     • It consists of usual circular & longitudinal layers
  4. External adventitia
     • It is dense fibrous tissue surrounding the muscle layer

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Question 10. Histology of Kidney
Answer:

Histology of kidney External structure:

• It is a bean shaped structure
• Its convex margin is placed laterally while concave margin is placed medially forming hilum
• Hilum leads into renal sinus
• Renal sinus is occupied by the upper expanded part of the ureter called renal pelvis
• Renal pelvis divides into
  1. Major calyces
  2. Minor calyces
     • Each major calyx divides into it
  3. Papilla
     • It is a projection of kidney tissue

Histology of kidney Internal structure:

• Kidney consists of
  1. Inner part called medulla
     • It consists of triangular areas called renal pyramid
     • Base of it is directed towards cortex & apex towards renal pelvis
  2. Outer part called cortex
     • It consists of
       1. Cortical arches/lobules
          • It is the tissue lying between the base of the pyramid & surface of the kidney
       2. Renal columns
          • It is the tissue lying between adjacent pyramids

Histology of kidney Lobe of kidney:

• Pyramid & the cortex around it constitute lobe

Question 11. Histology of Thymus
Answer:

• Thymus consists of right & left lobes joined by fibrous tissue
• Each lobe is about 2 mm in diameter
• It has outer cortex & inner medulla
• Each lobe has
  1. Capsule
     • Made up of connective tissue
  2. Septa
     • It passes from capsule which incompletely divides the lobe into lobules

Cells of Thymus:

1. Epithelial cells called epitheliocytes
   • They are flattened cells
   • They join to form sheets covering internal surface of capsule, surfaces of septa & surfaces of blood vessels
   • They lie deep in the lobule
     Functions:
   • Prevents antigen present in blood from reaching lymphocytes in thymus
   • Promotes Tcell differentiation & proliferation

Question 12. Histology of Hypophysis Cerebri
Answer:

• It is also called Pituitary gland
• It has been divided into
  • Anterior part pars anterior
  • Intermediate part pars intermedia
  • Posterior partpars posterior
• Pars posterior & infundibular stalk together forms neurohypophysis
• Pars anterior & pars intermedia forms adenohypophysis

Histology of hypophysis cerebriv Adenohypophysis:

Histology of hypophysis cerebri Pars anterior:

• It consists of cords of cells separated by Sinusoids
• It consists of following cells
  1. Chromophil
     • Contains brightly stained granules
     • It is further classified into

Histology of hypophysis cerebri Acidophil or Alpha Cells:

Alpha Cells Types:

Histology of hypophysis cerebri Basophil or beta cells:

Beta Cells Types:

2. Chromophobe cells

• Contains very few granules

Pars tuberalis:

• Histology of hypophysis cerebri Pars tuberalis Consists of:
  1. Undifferentiated cells
  2. Acidophil
  3. Basophil

Pars intermedia:

• It is poorly developed
• Contains colloid filled vesicles
• Some cells produce melanocyte stimulating hormone

Pars intermedia Cells:

• Beta cells
• Secretory cells
• Chromophobe cells

Pars intermedia Neurohypophysis:

Pars intermedia Pars posterior:

• It consists of numerous Unmyelinated nerve fibres
• These are axons of neurons
• There are supporting cells called Pituicytes between these axons
• These cells have long dendritic processes
• The pars posterior is associated with the release of

1. 1. Vasopressin
   2. Oxytocin

 

Question 13. Histology of Thyroid
Answer:

• It is covered by a fibrous capsule
• Septa extends from capsule into gland substance & divides it into
  lobules
• Each lobule is made up of follicles
• Follicle has a cavity filled with colloid
• Each follicle consists of
  1. Cells:
     1. Follicular cells
        • They line the follicles
        • They secrete T3 & T4 hormones They contains
          • Golgi complex
          • Lysosomes
          • Microtubules
          • Microfilaments
          • Secretory vacuoles
        • They vary in shape according to their activity
          • Normally Cells are cuboidal with moderate colloid
          • Inactive cell are flat with abundant colloid
          • Highly active cell are columnar with scanty colloid
  2. C cells or parafollicular cells
     • They are polyhedral cells with oval nuclei

Histology of thyroid Location:

• In between follicular cells & basement membrane.
• In connective tissue between the follicles

Histology of thyroid Contains:

• Granular endoplasmic reticulum
• Golgi complex
• Mitochondria
• Membrane bound Secretory granules
  Hormone secreted:
• Thyrocalcitonin

2. Connective tissue stroma

• It surrounds the follicles
• It contains capillary plexus, lymphatic capillaries & sympathetic nerves

Question 14. Histology of Suprarenal Gland
Answer:

• It is also called adrenal gland
• It is covered by connective tissue capsule
• Septa extends from capsule and divides the gland substance

Histology of Suprarenal Gland Parts:

1. Cortex:
   • It is made up of cells arranged in cords
   • Sinusoids intervene between the cords
   • Layers:
     1. Zona glomerulosa
        • Outermost layer
        • Consists 1/5th of cortex
        • Cells are arranged as inverted U shape
     2. Zona fasciculata
        • Cells are arrange in straight columns
        • Sinusoids intervene between columns
        • Consists 3/5th of cortex
     3. Zona reticularis
        • Consists 1/5th of cortex
        • Made up of cords that branch and anastomose

• • Secretions:

1. • • Aldosterone and deoxycorticosterone by cells of zona glomerulosa
     • Cortisone and cortisol by cells of zona fasciculata
     • Glucocorticoids and sex hormones by cells of zona reticularis
2. Medulla:
   • Cells shows yellow cytoplasm
   • Cells are columnar
   • Arranged in columns which are separated by wide sinusoids
   • Cytoplasm is basophilic
   • Secretions:
   • Secretes adrenaline and non adrenaline

Question 15. Histology of Large Sized Artery
Answer:

• Large sized arteries include the aorta, carotid arteries, subclavian, axillary, iliac artery
• The wall of it is made up of
  1. Tunica intima
     • It is innermost layer
     • It consists of
       • An endothelial lining
       • Thin layer of glycoprotein called nasal lamina
       • Subendothelial connective tissue containing elastic fibres
     • In it internal elastic lamina is not distinct as in medium sized artery
  2. Tunica media
     • It is made up of mainly elastic tissue
     • This tissue is arranged in the form of series of concentric membranes
     • Between these membranes there is presence of loose connective tissue
     • This layer is limited outside by external elastic lamina made up of elastic fibres
  3. Tunica adventitia
     • It is relatively thin containing large amount of elastic fibres
     • These fibres merge with the external elastic lamina

Question 16. Histology of Spleen
Answer:

• The surface of spleen is covered by a layer of periosteum
• Capsule occurs below it
• It is made up of fibrous tissue with abundant elastic tissue
• Trabeculae extends from the capsule and divides the substance into smaller divisions forming a network
• Spaces between the trabeculae contains a network of reticular fibres
• Cells present in reticulum are.
  • Fibroblasts
  • Macrophages
  • Lymphocytes
  • Blood vessels
• Splenic artery enters the trabeculae and divides into arterioles
• Each arterioles is surrounded by lymphocytes
• This constitute white pulp of spleen
• Blood flows into the spaces lined by reticular cells due to the adherence of the dilated portion of vesszi called ampulla with reticular cells
• The part of spleen which contains blood is called red pulp of spleen
• Blood from red pulp is collected by wide sinusoids to drain
• These sinusoids are lined by modified endothelium
• These endothelium cells are shaped like banana and known as stave cells
• These cells contains fibrils which help the cells to change their shape as per requirement
• Thus spleen consists of two parts
  • White pulp
  • Red pulp

Question 17. Histology of Submandibular Gland
Answer:

• Submandibular gland is a mixed salivary gland
• It contains both serous and mucous acini
  1. Serous cells:
     • They are darkly stained
     • Have rounded nuclei placed towards the base
     • They are arranged in the form of rounded acini or roughly pyramid
     • Base is towards basement membrane and apex towards lumen
     • Apex shows microvilli and pinocytotic vesicles
     • Lumen has intercellular secretory canaliculi
     • Cytoplasm contains
     • Small and homogenous secretory granules Prominent Golgi apparatus
     • Abundant rough endoplasmic reticulum Mitochondria
     • Lysosomes
     • Microfilaments
  2. Mucous cells:
     • They are lightly stained
     • Nucleus is flattened and present towards the basement membrane
     • Cells are arranged in form of tubules
     • Cells lining the tubules are columnar
     • Secretory granules are large and ill defined
  3. Demilunes/Crescents:
     • These are mucous cells covered by serous cells
     • They are present at the ends of mucous tubules

Question 18. Histology of Cartilage
Answer:

• Cartilage is modified connective tissue
• Histology of cartilage It consists of
  1. Cartilage cells called chondrocytes
     • They lie in lacunae
  2. Matrix
     • It consists of homogeneous ground substance within which fibres are embedded
       1. Ground substance
          • Made up of complex molecules containing proteins & carbohydrates
       2. Fibres
          • Chiefly composed of Type II collagen fibres

Question 19. Name the four sites where Hyaline Cartilage is present
Answer:

• Hyaline cartilage is present in the following
  1. Costal cartilage connecting ends of ribs to sternum.
  2. Articular cartilage present over articular surfaces of synovial joints
  3. Skeletal framework of larynx
  4. Wall of trachea & large bronchi
  5. Parts of nasal septum & lateral wall of nose
  6. Connecting epiphysis to diaphysis in bones of growing children

Question 20. Microscopic structure of Hyaline Cartilage
Answer:

• Hyaline cartilage is transparent so called hyaline cartilage
• Microscopic structure of hyaline cartilage It consists of:
  1. Intercellular substance
     • It is homogeneous
  2. Matrix
     • It prevents separation of cells
     • Helps to maintain them in groups called cell nests
  3. Ground substance
     • It resists compressive forces
     • It contains collagen fibres which resists tensional forces

Question 21. Histology of Elastic Cartilage
Answer:

• Its matrix contains numerous elastic fibres
• These fibres are arranged in a network
• They are viewed using special stains
• The surface of elastic cartilage is covered by perichondrium
• Elastic cartilage is seen in following sites:
  1. Skeletal basis of auricle
  2. Lateral part of external acoustic meatus
  3. Wall of medial part of auditory tube
  4. Epiglottis & two small laryngeal cartilages
  5. Apical part of arytenoid cartilage

Question 22. Histology of Compact Bone
Answer:

• Compact bone is made up of lamella
• These lamellae are arranged in concentric rings surrounding narrow
• Haversian canal
• Canal runs along the length of the bone
• These canals branch & anastomose with each other
• They also communicate with the marrow cavity & with the external surface of bone through channels called the canals of Volkmann
• This canal is occupied by blood vessels, nerve fibres & some cells
• Together Haversian canal & lamellae constitute Haversian system, also called osteon
• Compact bone consists of many such osteons separated by interstitial lamellae
• Near its surface lamellae are arranged parallel to the surface called circumferential lamellae

Question 23. What are different types of Epiphysis?
Answer:

1. Pressure epiphysis
   • These epiphysis are articular
   • They take part in joint formation
   • Example: Head of humerus, lower end of radius, etc.
2. Traction epiphysis
   • These epiphysis are non articular & so donot take part in joint formation
   • It provides attachment to tendons of muscle
   • Example: Tubercles of humerus
3. Atavistic epiphysis
   • They are independent but they become fused
   • Example: coracoid process of scapula
4. Aberrant epiphysis
   • They are unusual
   • Example: Epiphysis at the head of the 1st metacarpal bone & at the base of other metacarpal bone

Question 24. Draw & label a T.S. of an Osteon (or) Draw a well labelled diagram of Histology of thymus
Answer:

Question 25. Haversian system (or) Histology of parotid gland
Answer:

• The compact bone is made up of lamellae
• These lamellae are arranged in concentric rings surrounding narrow
• Haversian canal
• This canal is occupied by blood vessels, nerve fibres & some cells
• Together Haversian canal with lamellae constitute Haversian system

Question 26. Histology of Bone
Answer:

• Bone is a modified connective tissue
• Histology of bone It consists of:
  1. Osteocytes
     • They are widely separated by Intercellular substance
     • They lie in lacunae of bone
  2. Osteoblasts
     • They are bone forming cells
     • They are found lining surfaces of growing bone
  3. Osteoclasts
     • They are bone resorbing cells
     • They are found over surfaces where bone removal is taking place
  4. Osteoprogenitor cells
     • They resembles fibroblasts
  5. Bone lining cells
     • They are flattened cells present over bony surfaces

Question 27. Histology of large sized artery. (or) Histological appearance of elastic artery
Answer:

• Elastic arteries or largesized arteries include the aorta, carotid arteries, subclavian, axillary, iliac artery
• The wall of it is made up of:
  1. Tunica intima
     • Subendothelial connective tissue contains more elastic fibres
     • Internal elastic lamina is not distinct
  2. Tunica media
     • It is made up of mainly of elastic tissue
     • This tissue is in the form of a series of concentric membranes
     • Between these membranes there is presence of loose connective tissue
  3. Tunica adventitia
     • It is relatively thin containing large amount of elastic fibres
     • These fibres merge with the external elastic lamina

Question 28. Microscopic Structure of Spleen
Answer:

It is covered by a layer of peritoneum

• Capsule is present below it
• It is made up of fibrous tissue with abundant elastic fibres
• Trabeculae arises from the capsule & divides it into small divisions forming a network
• Lymph vessels are confined to the capsule & trabeculae
• Spaces between the trabeculae contains a network of reticular fibres

Cells present in reticulum:

• Fibroblasts
• Macrophages
• Lymphocytes
• Blood cells

Question 29. Histology of Lymph Node
Answer:

• They are small beanshaped structures scattered along the lymphatic vessels
• Lymph node is surrounded by capsule composed mainly of collagen fibres
• Lymph node consists of
  • Connective tissue framework
  • Cells
    1. L-ymphocytes
       • B-Lymphocytes
       • T-Lymphocytes
    2. Macrophages
    3. Fibroblasts
    4. Endothelial cells
    5. Pericytes & smooth muscle cells

Histology of lymph node Zones:

1. 1. Cortex-Outermost zone
   2. Medulla-Surrounding cortex

Question 30. Histology of Thymus
Answer:

• Thymus consists of right & left lobes joined by fibrous tissue
• Each lobe is about 2 mm in diameter
• It has outer cortex & inner medulla
• Each lobe has
  1. Capsule
  2. Septa

Histology of thymus Cells of thymus:

1. Epithelial cells called epitheliocytes
2. Lymphocytes
3. Macrophages
4. Corpuscles of Hassall

Question 31. Microscopic anatomy and development of Tonsil
Answer:

• It consists of diffuse lymphoid tissue containing lymphatic nodules
• It is covered by stratified Squamous epithelium
• This epithelium extends into tonsil forming several tonsillar crypts

Microscopic anatomy and development of tonsil Crypts:

• It contains numerous mucous glands
• It contains cells like
  1. Lymphocytes
  2. Desquamated epithelium cells
     • It also contains bacteria

Microscopic anatomy and development of tonsil Development:

Question 32. Microscopic structure of Trachea
Answer:

• It is made up of 16-20 tracheal cartilages
• The intervals between the cartilages are filled by fibrous tissue
• Gaps between cartilage end are filled in by smooth muscle & fibrous tissue
• Connective tissue in the wall contains many elastic fibres

Microscopic structure of Trachea Lumen:

• Lined by mucous membrane
• It consists of
  1. Epithelium
     • It is pseudostratified ciliated columnar
     • Microscopic structure of trachea It contains:
       1. Goblet cells
       2. Basal cells
       3. Lymphocytes
  2. Connective tissue contains
     • Elastic fibres
     • Serous & mucous glands
     • Lymphoid tissue
     • Eosinophil, leucocytes

Question 33. Histology of Submandibular Gland
Answer:

• Submandibular gland contains serous end peices & mucous tubules
• Serous end peices contains abundant secretory granules, spherical nucleus & basophilic cytoplasm
• Mucous secretory cells are filled with pale staining secretory material & little cytoplasm
• Its nucleus is compressed & contains densely stained chromatin
• The lumina of mucous tubules are larger
• The Intercalated & Striated ducts are less in number
• Connective tissue septa Mucous acini

Question 34. Histology of Liver
Answer:

• The liver is covered by capsule made up of connective tissue
• The liver substance is divided into large number of lobes consisting of numerous hepatic lobules
• The lobules appear to merge with one another
• Each lobule is made up of liver cells called hepatocytes
• These cells are large with round openfaced nuclei & prominent nucleoli
• They are separated by sinusoids
• Sinusoids are surrounded by reticular fibres
• Along the periphery of each lobules, there are angular intervals called portal canals
  • Each canal contains
  • Branch of portal vein
  • Branch of hepatic artery
  • Interlobular bile duct
• These structures collectively form portal triad

Question 35. Histology of pancreas (or) Islets of Langerhans
Answer:

• It is partly exocrine & partly endocrine gland
  1. Exocrine part
     • A delicate capsule surrounds the pancreas
     • Septa extends from capsule into the gland & divides it into lobules
       Secretory elements are long & tubular
     • The lining cells are triangular with spherical nuclei
     • Cytoplasm is basophilic & contains zymogen granules
  2. Endocrine part
     • It consists of numerous collection of cells called islets of Langerhans
     • Each islets is separated from the surrounding alveoli by a thin layer of reticular tissue

. Histology of pancreas Types:

Question 36. Histology of Kidney
Answer:

Histology of kidney External structure:

• It is a bean shaped structure
• Its convex margin is placed laterally while concave margin is placed medially forming hilum
• Hilum leads into renal sinus
• Renal sinus is occupied by the upper expanded part of the ureter called renal pelvis
• Renal pelvis divides into
  1. Major calyces
  2. Minor calyces
  3. Papilla

Histology of kidney Internal structure:

1. Kidney consists of
2. Inner part called medulla 2 Outer part called cortex

Question 37. Histology of Pituitary Gland
Answer:

• It is also called hypophysis cerebri
• It has been divided into
  • Anterior partpars anterior
  • Intermediate partpars intermedia
  • Posterior partpars posterior
  • Pars posterior & infundibular stalk together forms neurohypophysis
  • Pars anterior & pars intermedia forms adenohypophysis

Question 38. Adrenal Cortex Zone Fasciculatum
Answer:

• It is the middle layer of Suprarenal cortex
• It forms middle 3/5th of the cortex

Adrenal cortex zone fasciculatum Cells:

• They are arranged in straight columns
• Sinusoids intervene between them
• Cells are large, polyhedral
• Contains basophilic cytoplasm & vesicular nuclei
• They are rich in lipids & vitamin C
• They produce glucocorticoids

Question 39. Parathyroid glands
Answer:

• It is covered by a connective tissue capsule
• Septa extends from capsule & divides the gland substance

Arathyroid glands Cells:

1. Chief cells or principal cells

• They are numerous
• They are smaller in size
• Contains clear cytoplasm & vesicular nuclei
• They produce parathyroid hormone
  Types:
• Light
• Dark
• Clear

2. Oxyphilic/ eosinophilic cells

• They are absent in the young
• They are larger in size
• Contains granules in cytoplasm
• Nucleus is small & stains intensely

Question 40. Microscopic picture of Suprarenal Gland
Answer:

• Suprarenal gland is also called adrenal gland
• It is covered by a connective tissue capsule
• Septa extends from capsule & divides the gland substance

Microscopic picture of suprarenal gland Parts:

1. Superficial part called cortex

• It is made up of cells arranged in cords
• Sinusoids intervene between the cords
  Layers:
• Outermost layer called zona glomerulosa
• Next zone called zona fasciculata
• Innermost layer called zona reticularis

2. Deeper part called medulla

• Its cells shows yellow granules in the cytoplasm
• The cells are columnar
• Cytoplasm is basophilic
• They secrete noradrenaline & adrenaline

Question 41. Give the microscopic structure of Developing tooth Collagen Fibres Golgi apparatus
Answer:

Developing tooth Collagen fibres Golgi apparatus Developing tooth:

• The epithelium in relation to the alveolar process thickens to form dental lamina
• The cells of dental lamina proliferate at various sites to form enamel organ
• This enamel organ grows into underlying mesenchyme & assumes cup shaped appearance
• The mesenchyme is of neural crest origin & is called dental papilla
• The dental papilla alongwith enamel organ is called tooth germ
• This stage is called ‘cap stage’
• The cells of enamel organ adjacent to dental papilla becomes columnar & are known as ameloblasts
• The mesenchymal cells adjacent to ameloblasts differentiate into odontoblasts
• The two cell layers are separated by a basement membrane
• Rest of mesenchymal cells form pulp
• This is called ‘bell stage’
• Ameloblasts lay down enamel & odontoblasts lay down dentin
• The root of the tooth is formed by laying down of layers of dentin & narrowing the pulp space
• The root dentin is covered by mesenchymal cells that differentiate into cementoblasts
• These cementoblasts lay down cementum

Developing tooth Collagen fibres Golgi apparatus Collagen fibres:

• Each collagen fibre is made up of fibrils of diameter 20200 nm
• Each fibrils shows cross striations
• Each fibrils contains numerous myofibrils
• Size of each collagen fibre is about 112 micrometer in diameter They are arranged in groups

Developing tooth Collagen fibres Golgi apparatus Types:

Developing tooth Collagen fibres Golgi apparatus Golgi apparatus:

• It is small, irregular structure

Developing tooth Collagen fibres Golgi apparatus Location:

• Usually near the nucleus

Developing tooth Collagen fibres Golgi apparatus Structure:

• It is made up of membranes
• Membranes form the walls of a number of flattened sacs that are placed over one another
• Towards the margins there are small rounded vesicles

Developing tooth Collagen fibres Golgi apparatus Regions:

• Functionally, Golgi apparatus is divided into 3 regions

1. Cis face/ Cis Golgi

• It is a region near to the nucleus

2. Trans face/ Trans Golgi

• It is a region near cell membrane

3. Intermediate part

• It is present between cis & trans face

Question 42. Microscopic picture of endochondrial ossification
Answer:

• Following changes occurs during endochondrial ossification
• Mesenchymal cells are closely packed to form Mesenchymal condensation
• Some of them differentiate into chondrocytes & lay down hyaline cartilage
• Cells of this cartilage are
  1. Initially-small & irregular
  2. Later-Enlarges
     • Next, due to lack of nutrition, cells die forming empty spaces called primary areolae
     • This is later destroyed by the blood vessels of perichondrium & results in secondary areolae
     • Osteoprogenitor cell invade it & becomes osteoblasts
     • Osteoblasts lay down a layer of osteoid
     • Osteoid is calcified & forms lamellus of bone
     • Similarly, osteoblasts lay down another layer of lamellus which gets calcified
     • Some osteoblasts are entrapped between the two lamellae & becomes osteocytes Osteocyte

Question 43. Histology of skeletal muscle
Answer:

• The muscle present in relation to bony skeleton is called skeletal muscle
• Histology of skeletal muscle It is made up of:

1. 1. Muscle fibres
      • They are long and cylindrical
      • They are arranged in bundles called fasciculi
      • Each muscle fibre is covered by a plasma membrane called sarcolemma
   2. Connective tissue
      • It supports and unites muscle fibres

Histology of skeletal muscle Striations:

• Skeletal muscle section on staining shows alternate dark and light band

1. 1. A band dark band
   2. I band-light band
   3. Z band-dark line between I band
   4. H band-light line between A band
   5. M band dark line in center of H band

• Part present between two consecutive Z bands is called sarcomere.

Question 44. Primary cartilaginous joint
Answer:

• Primary cartilaginous joints are also known as synchondroses
• These bones are connected by hyaline cartilage
• Sometimes occur between ossification centres
• This cartilage may ossify with age
• Such joints allow only a little movement such as in spine and ribs.

Question 45. Histology of thyroid gland
Answer:

• Thyroid gland is covered by fibrous capsule
• Septa extends from capsule into gland substance and divides it into lobules
• Each lobule is made up of follicles
• Follicle has a cavity filled with colloid
• Each follicle consists of:

1. 1. Cells
      1. Follicular cells
         • They line the follicle
         • Secretes T3 &T4 hormones
         • They vary in shape according to their activity
      2. C cells or parafollicular cells
         • They are polyhedral in shape
         • Present between follicular cells and basement membrane and between the follicles
   2. Connective tissue stroma
      • It surrounds the follicles
      • Contains capillary plexus, lymphatic capillaries and sympathetic nerves