Lymph node, spleen, thymus, tonsil- discussion, viva

Lymphatic system:

1. What is the function of lymphatic system?
• The function of lymphatic system is immunity / to protect the organism from invading pathogens or antigens
2. What are the components of lymphatic system?
• Cells- distributed throughout the body as single cells or aggregations of cells or non-encapsulated lymphatic nodules
• Lymphatic organs- lymph node, spleen, thymus, tonsil
3. Name the lymphatic organs surrounded by connective tissue capsule
• Lymph node, spleen, thymus
4. Name the lymphatic organ covered by epithelium
• Tonsil

Lymph node:

1. What are the parts of lymph node?
• Outer cortex- network of reticular fibers, non-encapsulated aggregations of lymphocytes called lymphatic nodules with pale germinal center
• Inner medulla- medullary cords (irregularly arranged lymphocytes, macrophages, plasma cells in network of reticular fibers) and medullary sinuses
2. What is direction of flow of lymph?
• Afferent lymphatic vessel--subcapsular sinus--trabecular sinus--medullary sinus--efferent lymphatic vessel
3. What is the function of lymph node?
• The function of lymph node is to filter the lymph as it enters the lymph node
4. What are lymph sinuses?
• Lymph sinuses are the spaces with fine network of reticular fibers filled with lymph
• Subcapsular sinus- sinus present beneath the connective tissue capsule
• Trabecular sinus- sinus present around the connective tissue septa (trabeculae) entering the lymph node
• Medullary sinus- sinus present in the medulla
5. What are germinal centers?
• The germinal centers are the pale regions in the center of lymphatic nodule which represent the active sites of lymphocyte proliferation

Spleen:

1. What are the parts of spleen and their components?
• Red pulp- splenic cords of Billroth (network of reticular fibers with macrophages, lymphocytes, plasma cells, blood cells) and splenic/blood sinuses
• White pulp- dark staining lymphoid aggregations/nodules surrounding a central artery. Along with lymphocytes, antigen-presenting cells and macrophages are also seen
2. What is the function of red pulp?
• The function of red pulp is to filter the blood. It removes the antigens, microorganisms, platelets and aged or abnormal erythrocytes from the blood.
3. Is there a germinal center in the lymphatic nodule present in spleen?
• Yes
4. What are the types of lymphatic cells seen in white pulp?
• T cells- surround the central arteries
• B cells- present in rest of lymphatic nodule
5. What are the functions of spleen?
• Fetal life- produces granulocytes and erythrocytes
• Important reservoir for blood
• Filters blood
• Takes part in immunity
6. Is spleen essential for life?
• No, it is not

Thymus:

1. Where is thymus located?
• Thymus is located in the root of neck and upper anterior mediastinum
2. What are the stages of thymus?
• Childhood- most active upto puberty
• After puberty- undergoes involution
• Adults- replaced with adipose tissue
3. What are the parts of thymus?
• Connective tissue capsule divides the thymus into incomplete thymic lobules. Each thymic lobule has peripheral cortex and inner medulla which is continuous with adjacent lobules
• Cortex- densely packed lymphocytes
• Medulla- few lymphocytes, more epithelial reticular cells, thymic/Hassall's corpuscles
4. What are Hassall's corpuscles?
• They are oval structures consisting of round or spherical aggregations of flattened epithelial cells around the calcified or degenerating mass of epithelial cells
5. What are the functions of epithelial reticular cells?
• The epithelial reticular cells forms the blood-thymus barrier and secretes hormones necessary for proliferation, differentiation and maturation of T-cells
6. What happens to the child if thymus is removed?
• The child may not be able to fight pathogens and death may occur as a result of infection and lack of functional immune system
7. What are the hormones secreted by epithelial reticular cells?
• Thymulin, thymopoietin, thymosin, thymic humoral factor, interleukins, interferon
8. Name the layers forming blood-thymic barrier?
• Endothelial cells
• Epithelial reticular cell
• Macrophages

Tonsil:

1. Where is tonsil located?
• Tonsil is located at the oro-pharyngeal isthmus on either side of oral cavity
2. What are the parts of tonsil?
• Attached surface- covered by connective tissue capsule
• Free surface- covered by stratified squamous non-keratinized epithelium which invaginates into the tonsil as tonsillar crypts
• Tonsillar crypts are surrounded by numerous lymphatic nodules

Blood vessels- discussion, viva

Circulatory system/ Vascular system/ Blood vessels:

1. Name two parts of circulatory system
• Blood vascular system and lymph vascular system
2. Name the 3 layers of blood vessels
• From inside out- tunica intima, tunica media, tunica adventitia
3. What are the components of tunica intima?
• endothelium- simple squamous epithelium 
• subendothelial connective tissue
• internal elastic lamina
4. What are the components of tunica media?
• smooth muscle fibers
• elastic fibers
• reticular fibers
5. What are the components of tunica adventitia?
• connective tissue (collagen, elastic fibers)
• blood vessels/ vasa vasorum
• nerves
• lymphatics
6. Name the smallest blood vessels
• Capillaries, venules
7. Name the different types of capillaries
• Continuous capillaries- endothelial cells join and form uninterrrupted solid endothelial lining. Seen in muscle, skin, connective tissue, nervous tissue, respiratory organs
• Fenestrated capillaries- pores/ fenestrations present in the cytoplasm of endothelial cells for rapid exchange of molecules. Seen in endocrine tissues and glands, small intestine, kidney
• Sinusoidal capillaries- wide gaps present inbetween endothelial cells. Seen in liver, spleen and bone marrow
8. Name the three types of arteries in the body
• Elastic/ large arteries
• Muscular/ medium sized/ distributing arteries
• Arterioles
9. What are the general differences between arteries and veins?
• lumen is intact in artery and collapsed in vein
• the wall of the artery is thicker than the wall of the vein
• tunica media is thick in the artery, tunica adventitia is thick in the vein
• well developed internal and external elastic laminae present in the artery, absent in the vein

Medium sized artery:

1. What is the composition of tunica intima?
• Endothelium- simple squamous epithelium
• Subendothelium- loose connective tissue
• Internal elastic lamina- prominent
2. What is the composition of tunica media?
• Equally thick as tunica adventitia with various amounts of reticular  and elastic fibers, abundant  smooth muscle fibers 
3. What is the composition of tunica adventitia?
• Thickness equal compared to tunica media composed of collagen and elastic connective tissue fibers, blood vessels, nerves and lymphatics
4. What is vasa vasorum?
• These are the small blood vessels supplying the walls of large blood vessels to provide nutrition to tunica media and adventitia
5. Give examples for medium sized artery
• Brachial artery, radial artery, ulnar artery, femoral artery, popliteal artery, etc

Large artery/ Elastic artery:

1. Give examples for large artery
• Aorta, brachiocephalic artery, common carotid artery, subclavian artery, vertebral artery, common iliac artery, pulmonary trunk
2. Why elastic artery has more of elastic fibers?
• The elastic fibers provide great resilience and flexibility during blood flow
3. Name the layers of the blood vessel
• From inside out- tunica intima, tunica media, tunica adventitia
4. What is the composition of tunica intima?
• Endothelium- simple squamous epithelium
• Subendothelium- loose connective tissue
5. What is the composition of tunica media?
• Very thick with various amounts of reticular  and smooth muscle fibers, abundant elastic fibers present in the form of laminae
6. What is the composition of tunica adventitia?
• Thin compared to tunica media composed of collagen and elastic connective tissue fibers, blood vessels, nerves and lymphatics
7. What is vasa vasorum?
• These are the small blood vessels supplying the walls of large blood vessels to provide nutrition to tunica media and adventitia

Large vein:

1. What is the composition of tunica intima?
• Endothelium- simple squamous epithelium
• Subendothelium- loose connective tissue
2. What is the composition of tunica media?
• Thin layer with various amounts of reticular  and elastic fibers, smooth muscle fibers 
3. What is the composition of tunica adventitia?
• Very thick compared to tunica media composed of collagen and elastic connective tissue fibers, blood vessels, nerves, lymphatics and longitudinally arranged smooth muscle fibers. 
4. What is vasa vasorum?
• These are the small blood vessels supplying the walls of large blood vessels to provide nutrition to tunica media and adventitia
5. Give examples for large sized vein
• Portal vein, inferior venacava, superior venacava
6. Give the differences between arteries and veins

• Types	Medium sized artery	Large artery	Large vein
  Tunica intima: Endothelium Subendothelial CT Internal elastic membrane (fenestrated membrane of Henle)	Endothelial cells with basal lamina. Sparse. Well defined wavy structure.	Thick lining endothelium with basal lamina. Well defined with collagen and elastic fibers and smooth muscle cells. Fibroblasts absent. Present, Not distinct.	Endothelial layer with basal lamina. Thin, but also with smooth muscle cells. Not distinct.
  Tunica media External elastic lamina	Mainly of smooth muscle cells with intervening collagen, reticular and elastic fibers. Few or no fibroblasts Prominent	Thickest of the 3 layers. Abundant elastic fibers with intervening smooth muscle cells, collagen fibers and ground substance. Elastic fibers in the form of membranes. Not distinct	Thin consisting of smooth muscle cells, collagen fibers and fibroblasts. Not distinct
  Tunica adventitia	As thick as tunica media. Mainly collagen fibers. Adjacent to tunica media form prominent external elastic lamina.	Less than half the thickness of tunica media. Mainly of collagen fibers with loose network of elastic fibers. Fibroblasts and macrophages present. Vasa vasorum seen.	Thickest of the 3 layers  consisting of longitudinally running smooth muscle cells.  Fibroblasts, collagen and elastic fibers seen. Vasa vasorum extends up to the tunica media.
  Lumen	Round and intact.	Round and intact.	Collapsed and irregular. Larger lumen than the artery.
  E.g.	Radial, ulnar, tibial.	Aorta, pulmonary trunk.	Superior vena cava, inferior vena cava, portal vein.

Please refer the above table for the questions given below:

What are muscular arteries and elastic arteries? What is the functional significance of each layer in the wall of the vessel

What are the differences in the structure between the aorta (large artery) and any medium sized artery

What are the features in the structure of the inferior venacava (large vein)

Give the differences in the structure between large artery and vein

Give the differences between the medium sized artery and vein

Give examples for muscular artery and elastic artery

Peripheral nerve, sympathetic ganglia, spinal ganglia- discussion, viva

Peripheral nerve:

1. What are the components of nervous tissue?
• The components of nerve tissue are neurons, nerve fibers and neuroglia
2. What are the parts of nervous tissue?
• Peripheral nervous tissue and central nervous tissue
3. What are the components of peripheral nerve tissue?
• Cranial nerves, peripheral nerves, sympathetic ganglia, spinal ganglia
4. Name the cells involved in myelination of peripheral nerve? 
• Schwann cells
5. What is node of Ranvier? What is its function
• Node of Ranvier is the gap present between two adjacent Schwann cells
• It helps the impulses to jump from one internode to another and helps in faster conduction of impulses
6. What are ganglia?
• Ganglia are the aggregations of cell bodies outside the central nervous system
7. What are the different types of neuroglia in peripheral nervous system?
• Schwann cells and satellite cells
8. What are the connective tissue layers covering the peripheral nerve?
• Epineurium: It is the strong dense irregular connective tissue sheath binding all the fascicles 
• Perineurium: It is a thin connective tissue surrounding the individual fascicle
• Endoneurium: It is the loose vascular connective tissue with reticular fibers surrounding the myelinated axon or cluster of unmyelinated axons
9. What is the constitution of the neurolemma sheath, Myelin sheath and Axis cylinder. What are the nerve fibrils
• Neurolemma sheath- the cytoplasm and nucleus of Schwann cell lying outside the myelin sheath
• Myelin sheath- the modified cell membrane of Schwann cell wrapped around the axon
• Axis cylinder- axon
• Nerve fibril- a delicate fibril found in the cell body and processes of a neuron
10. In what situation is the neurolemma sheath absent?
• Neurolemma sheath is absent in central nervous system
11. What is neuroglia? What are the cell types in it
• Neuroglia are the supporting cells present in the nervous system
• Cell types:
• CNS- ependyma, astrocytes, oligodendrocytes
• PNS- Schwann cells, satellite cells
12. What is axon hillock?
• Axon hillock is a special part present between the cell body and axon. It is devoid of nissl granules
13. Difference between thick and thin fiber in PNS
• Thick fiber- it is myelinated and helps in faster conduction of the impulses
• Thin fiber- it is unmyelinated and helps in slow and uniform conduction of impulses

Spinal / sensory ganglion:

1. Where is spinal ganglion situated?
• Spinal ganglion is situated on the dorsal root of spinal nerve, sensory ganglion of 5, 7, 9 and 10 cranial nerves
2. What are the other names for spinal ganglion?
• Dorsal root ganglion, sensory ganglion
3. What are the identifying features of spinal ganglion?
• Large, round pseudounipolar neurons of different sizes arranged peripherally in groups 
• Single nucleus placed in center of neuron
• Bundles of nerve fibers running between the groups of neurons
• More number of satellite cells surround the neurons
4. Give the examples for spinal ganglion
• Dorsal root ganglia of spinal nerves, sensory ganglia of cranial nerves 5, 7, 9, 10.
5. What are the functions of satellite cells?
• The satellite cells provide the structural and metabolic support to the neurons and insulate the neurons
6. What are pseudo ganglia?
• Localized thickening of the nerve trunk without cell bodies and having only nerve fibers
7. What are the differences between spinal and sympathetic ganglia?
• Refer the table below

 Sympathetic / autonomic ganglion:

1. Where is sympathetic ganglion situated?
• Sympathetic ganglion is situated along the sympathetic trunk and parasympathetic ganglia (ciliary, otic, pterygopalatine, submandibular)
2. What is the other name for sympathetic ganglion?
• Autonomic ganglion
3. What are the identifying features of sympathetic ganglion?
• Small, irregular shaped, uniform size, scattered multipolar neurons
• Nucleus placed eccentrically in the neuron
• Nerve fibers are irregularly arranged separating the neurons
• Few satellite cells arranged around the multipolar neurons
4. Give examples for sympathetic ganglion
• Sympathetic ganglia along sympathetic chain, otic ganglion, ciliary ganglion, submandibular ganglion and pterygopalatine ganglion
5. What are the functions of satellite cells?
• The satellite cells provide the structural and metabolic support to the neurons and insulate the neurons
6. What are the differences between the sympathetic and spinal ganglion?
• Refer the table below

Type	Spinal ganglia	Autonomic ganglia
Capsule	Thick.	Thin.
Neurons	Peripherally arranged, large and round pseudo-unipolar neurons.	Irreguarly arranged multipolar neurons appear star shaped and are of varying sizes in sections.
Nerve fibers	Bundles of nerve fibers separate the neurons. Regularly arranged fibers enter and leave the ganglion.	Axons and dendrites pass through the widely spaced neurons, without being involved in synapses. Irregularly scattered nerve fibers.
Satellite cells	A layer of small cuboidal cells envelopes the neurons.	Few satellite cells incompletely surround the cell body.
E.g.	Dorsal root ganglia of the spinal nerves, sensory ganglia of cranial nerves (V, VII, IX, X).	Sympathetic ganglia along sympathetic chain, Otic/ ciliary/ Submandibular/ pteryogopalatine ganglia.

Muscle tissue- discussion, viva

Muscle tissue:

1. What are the types of muscle tissue based on histology?
• Skeletal muscle, cardiac muscle, smooth muscle
2. What is sarcolemma, sarcoplasm?
• The cell membrane or the plasma membrane of the muscle fiber is called as sarcolemma and the cytoplasm of the muscle fiber is called as sarcoplasm
3. What are myofibrils?
• Myofibrils are composed of myofilaments (contractile proteins) actin and myosin and are present in the sarcoplasm of the muscle fiber
4. Myofilamentsàmyofibrilsà muscle fibersàmuscle fascicles/ bundlesàmuscle

Skeletal muscle:

1. What are the identifying features of skeletal muscle?
• Voluntary, Long, cylindrical, unbranched muscle fiber
• Multinuclei present deep to sarcolemma at the periphery of the muscle fiber
• Distinct cross-striations are seen
2. Why is it called as striated muscle?
• It is called as striated muscle because of the cross-striations which are seen as light I-band and dark A-band under light microscope
3. What are cross-striations?
• Cross-striations are formed due to the regular arrangement of the actin and myosin. under light microscope they are seen as light I-bands and dark A-bands
4. What is sarcomere?
• Sarcomere is the smallest contractile unit present between two adjacent Z-lines. They are repeated throughout the entire length of each myofibril
5. What are the coverings of skeletal muscle? or Give the connective tissue arrangements in C.S of skeletal muscle
• Epimysium: outer dense irregular connective tissue covering of the muscle
• Perimysium: less dense irregular connective tissue covering the bundles of muscle fibers
• Endomysium: thin layer of reticular connective tissue covering each muscle fiber
6. What is syncytium?
• Syncytium is a multinucleated cell that results from multiple cell fusions of uninuclear cells
7. What are the structures present along with connective tissue sheaths?
• Blood vessels, nerves and lymphatics
8. What are the features of the muscle fiber in cross-section?
• All the fibers are all most same in size
• One or two nuclei seen in each muscle fiber deep to sarcolemma
• Cross-sections of myofibrils observed
• Surrounding each fiber is the connective tissue sheath endomysium, blood vessels, nerves and lymphatics
9. What are the features of skeletal muscle in longitudinal section?
• Section of each long, cylindrical unbranched muscle fibers
• Multinuclei present deep to sarcolemma
• Cross-striations seen as light I-band and dark A-band
10. What are cross-striations?
• Cross-striations are the light (I band) and dark (A) bands observed under light microscope due to regular arrangement of protein filaments actin and myosin
11. What are motor end plates?
• Motor end plates or neuromuscular junctions are the sites where impulse from axon is transmitted to the skeletal muscle fiber
12. What is present between the individual muscle fibers?
• Connective tissue sheath endomysium with blood vessels, nerves and lymphatics
13. Give examples for skeletal muscle?
• All muscles attached to bones. Flexor pollicis longus, deltoid etc.
14. What are the differences between skeletal muscle and cardiac muscle?
• Refer the table below
15. What are the differences between skeletal muscle and smooth muscle?
• Refer the table below

Cardiac muscle:

1. What are the characteristic features of cardiac muscle?
• Cardiac muscle is involuntary, short, cylindrical, branched fibers
• One or two nuclei present in the center of the fiber
• Cross-striations and intercalated discs seen
2. What are cross-striations?
• Cross-striations are the light I-band and dark A-band observed under light microscope due to regular arrangement of protein filaments actin and myosin
3. What are intercalated discs?
• Intercalated discs are characteristic features of cardiac muscle
• They are the junctional complexes present between the adjacent muscle fibers
• The gap junction in the intercalated disc enable ionic communication and continuity between adjacent cardiac muscle fibers
4. Give examples of cardiac muscle
• Walls and septa of heart, walls of large vessels (aorta, pulmonary trunk) attached to heart
5. What are the differences between cardiac muscle and skeletal muscle?
• Refer the table below
6. What are the differences between cardiac muscle and smooth muscle?
• Refer the table below

Smooth muscle:

1. What are the characteristic features of smooth muscle?
• Involuntary, non-striated, spindle shaped fibers
• Single nucleus present in the center of the muscle fiber
2. Do the smooth muscle fibers contain actin and myosin?
• Yes, the fibers contain actin and myosin
3. Why is it called as non-striated or smooth muscle fibers?
• The myofilaments actin and myosin are not arranged regularly as in skeletal and cardiac muscle. So they appear smooth
4. What are the features observed in cross-section?
• They are present in small fascicles
• The size and shape of each fiber varies depending on the plane of section passing through the fiber
• If the plane passes through the center of the fiber, the section is larger with large central nucleus
• If the plane passes at the tapered end of the fiber, the section is very small without nucleus
• If the plane passes between the two, the fiber appears small with smaller nucleus
5. Give examples for smooth muscle fibers
• Walls of visceral hollow organs like respiratory, GIT, urinary tract, reproductive tracts and blood vessels
6. What are the differences between smooth muscle and skeletal muscle?
• Refer the table below
7. What are the differences between smooth muscle and cardiac muscle?
• Refer the table below

	Skeletal muscle	Cardiac muscle	Smooth muscle
Muscle cells (fibers)	Long cylindrical un-branched muscle fibers.	Tubular fibers branch and anastomoses.	Spindle shaped.
Striations	Cross striations of alternating light (Isotropic or I bands) and dark bands (Anisotropic or A bands). Light band bisected by a dark transverse line, the Z line. Dark band shows the lighter zone in center, the H band.	Faint cross-striated banding patterns.	Lack visible cross striations.
Nuclei	Multinucleated, flat or oval, peripherally arranged.	Uni-nucleate, central in position.	Uni-nucleate, central in position.
Distinguishing feature	Sarcomere, the smallest repetitive subunit of the contractile apparatus lies between two Z lines. Sarcomere consists of thick and thin filaments. Thick filament mainly composed of myosin and thin filament actin  tropomyosin and troponin.	Intercalated disk, faintly seen, under the light microscope, represent the junctional complexes.	-
Functions	Movements.	Autonomic, rhythmic, involuntary movements.	Involuntary movement - i.e. churning of food, movement of urine from the kidney to the bladder, parturition of the fetus.
E.g.	Muscles attached to the bone.	Heart.	Walls of hollow organs (stomach, intestine, uterus, ureter).

Bone LS, Bone TS- discussion, viva

Bone:

1. What is bone?
• Bone is a specialized connective tissue.
2. What are the components of bone?
• Bone consists of cells (osteoblast, osteocyte, osteoclast), fibers and extracellular matrix.
• Extracellular matrix- 
• organic (coarse type I collagen fibers, sulfated glycosaminoglycans, hyaluronic acid, glycoproteins
• inorganic- calcium and phosphate together form hydroxyapatite crystals
3. Why is bone hard?
• Bone is hard because of mineral deposition in the matrix. The hydroxyapatite crystals with collagen fibers makes the bone hard, durable and strong.
4. What are the functions of bone?
• Bone is remodeled continuously due to mechanical stress, bone thinning due to age, fracture healing
• Calcium and phosphate are released into blood when needed to maintain proper levels
• Calcium is necessary for muscle contraction, blood coagulation, cell membrane permeability, transmission of nerve impulses
5. What are the functions of the bone cells?
• Osteoblast- synthesize, secrete and deposit osteoid (uncalcified without minerals)
• Osteocytes- mature cells trapped in bone matrix
• Osteoclasts- large multinucleated cells, responsible for resorption (renew or restructure), remodeling of the bone and bone repair

Bone Longitudinal Section:

1. What is the arrangement of bone components in LS of bone?
• Haversian canals coarse longitudinally with parallely running lamellae, lacunae, canaliculi
2. What is the function of Haversian canal and Volkmann's canal?
• Nutrition to the bone is supplied through blood vessels present in the Haversian canals and Volkmann's canals. Along with blood vessels, nerves and lymphatics are also present
3. What is a lamella, lacuna, canaliculi?
• Lamella- thin plate of bone matrix 
• Lacuna- space lodging osteocyte
• Canaliculi- tiny canals radiating from lacuna, penetrate lamellae and communicate with other canaliculi. They lodge the cytoplasmic processes of osteocytes which communicate with cytoplasmic processes of other osteocytes.

Bone Transverse Section:

1. What is osteon/ Haversian system?
• One Haversian system consists of Haversian canal with neurovascular structures in the center surrounded by concentric lamellae
2. What are the different types of lamellae?
• Concentric lamellae- lamellae surrounding the Haversian canal
• Interstitial lamellae- lamellae present between the various osteons
• Inner circumferential lamellae- lamellae present surrounding the bone marrow/endosteum
• Outer circumferential lamellae- lamellae present deep to the periosteum
3. What is periosteum?
• Periosteum is the connective tissue which surrounds the bone
• It has two layers outer fibrous layer and inner cellular layer
• Outer fibrous layer- formed by collagen fibers and fibroblasts
• Inner cellular layer- formed by the osteoprogenitor, osteoblast cells
4. What is a lamella, lacuna, canaliculi?
• Lamella- thin plate of bone matrix 
• Lacunae- spaces present between adjacent lamellae lodging osteocytes
• Canaliculi- tiny canals radiating from lacuna, penetrate lamellae and communicate with other canaliculi. They lodge the cytoplasmic processes of osteocytes which communicate with cytoplasmic processes of other osteocytes.
5. What is Haversian canal and Volkmann's canal?
• Haversian canal- Central canal of the osteon running longitudinally which transmits blood vessels, nerves and lymphatics to provide nutrition to the bone
• Volkmann's canal- communicating channels between the Haversian canals, periosteum and endosteum
6. What are Howship's lacunae?
• They are eroded shallow depressions which lodges osteoclasts