AN70.1-AN71.2 | Glands & Lymphoid tissue — Gate Quiz

Correct! Serous acini (as in the parotid gland) are composed of pyramid-shaped cells with basophilic (darkly staining) cytoplasm containing zymogen granules, round centrally placed nuclei, and a very narrow lumen. The basal cytoplasm is basophilic due to abundant rough ER producing digestive enzymes.

Parotid = purely serous. Sublingual = predominantly mucous. Submandibular = mixed. Serous cell ID: dark, pyramid-shaped, round central nucleus, narrow lumen. Mucous cell ID: pale, vacuolated, flat basal nucleus, wide lumen.

Incorrect. Pale vacuolated cells with flattened basal nuclei describe mucous acini. Serous demilunes are seen in mixed glands (submandibular). The parotid is purely serous — all acini are serous.

Correct! Minor salivary glands of the palate are purely mucous. The parotid and lacrimal glands are purely serous. The submandibular gland is a mixed gland (predominantly serous with mucous acini and serous demilunes).

Minor salivary glands scattered throughout the oral mucosa (lips, palate, tongue, cheeks) are mostly mucous. They provide continuous surface lubrication. Major glands: Parotid (serous), Submandibular (mixed), Sublingual (mucous).

Incorrect. Parotid = purely serous; Submandibular = mixed; Lacrimal = serous. Purely mucous glands are found in the palate, lips, and tongue (minor salivary glands) and the sublingual gland.

Correct! The paracortex (deep cortex) of lymph nodes is the T-cell zone. It contains T lymphocytes and high endothelial venules (HEVs) — specialised post-capillary venules through which naive lymphocytes recirculate from blood into the node.

Lymph node zones: Outer cortex (B cell follicles) → Paracortex (T cells, HEVs) → Medulla (plasma cells in cords, macrophages in sinuses). DiGeorge syndrome (thymic aplasia) → depleted paracortex (T cell deficiency). X-linked agammaglobulinaemia → depleted follicles (B cell deficiency).

Incorrect. B cells form follicles in the outer cortex. Plasma cells are in medullary cords. Macrophages trap antigens in subcapsular sinuses. The paracortex = T cells + HEVs.

Correct! The spleen has no afferent lymphatics — blood enters via the splenic artery, flows through the white pulp (lymphoid) and then through the sinusoidal red pulp (where old RBCs are filtered by macrophages), and exits via the splenic vein. The red pulp sinusoids with Billroth's cords are the structural correlate of blood filtration.

Spleen: No afferent lymphatics. Blood filters through red pulp (Billroth's cords + venous sinusoids) → destroys old/abnormal RBCs, removes encapsulated bacteria. Lymph node: Multiple afferent lymphatics → subcapsular sinus → cortex → efferent lymphatic. Splenomegaly in malaria = red pulp congestion + activated macrophages.

Incorrect. Both spleen and lymph nodes have fibrous capsules and trabeculae, lymphoid follicles, and organised zones. The key distinguishing feature is the absence of afferent lymphatics and the presence of sinusoidal red pulp in the spleen.

Correct! Hassall's corpuscles (concentric whorls of degenerating epithelial reticular cells) in the medulla are pathognomonic of the thymus. The thymus has a densely lymphocytic cortex and a less dense medulla with Hassall's corpuscles. It is maximal in size at puberty.

Thymus ID on histology: (1) Cortex densely packed with thymocytes. (2) Medulla with fewer cells. (3) Hassall's corpuscles = concentric epithelial whorls in medulla. Also: blood-thymus barrier in cortex (not medulla); no follicles with germinal centres.

Incorrect. Hassall's corpuscles are unique to the thymus — this is the single most important histological identification feature. No other lymphoid organ has epithelial whorls in its medulla.

Correct! The Haversian canal at the centre of each osteon contains blood vessels (capillaries/venules) and nerve fibres, providing nutrition to the surrounding osteocytes via canaliculi. Volkmann's canals connect adjacent Haversian canals and penetrate from the periosteal surface.

Osteon structure: Central Haversian canal (vessels + nerves) → concentric lamellae → osteocytes in lacunae → canaliculi connecting lacunae. Interstitial lamellae = remnants of old osteons. Circumferential lamellae = at periosteal and endosteal surfaces.

Incorrect. Osteocytes occupy lacunae within the concentric lamellae surrounding (not in) the Haversian canal. Osteoclasts are on resorbing bone surfaces. Yellow marrow is in the medullary cavity, not Haversian canals.

Correct! Woven (primary/immature) bone has randomly oriented collagen fibres and is the first bone formed during fracture repair (as well as in embryonic bone formation and Paget's disease). It is mechanically weaker than lamellar bone and is gradually replaced by lamellar bone during bone remodelling.

Fracture healing sequence: haematoma → granulation tissue → soft callus (fibrocartilage) → hard callus (woven bone) → remodelling (lamellar bone restoration). Woven bone is always temporary; it is remodelled into lamellar bone by coupled osteoclast-osteoblast activity.

Incorrect. Lamellar bone (mature) has parallel collagen fibre arrangements in lamellae — this is the normal adult bone. Cortical and cancellous bone are both forms of lamellar bone differing in density. Woven bone is identified by random collagen arrangement.

Correct! Elastic cartilage contains type II collagen plus elastic fibres (visible with elastic stain — Verhoeff's or orcein). It is present in the epiglottis, auricle (pinna), Eustachian tube, and external auditory meatus. It has a perichondrium. Gross appearance: yellow (from elastin).

Cartilage ID: Hyaline = glassy, type II collagen, perichondrium (except articular). Elastic = type II + elastic fibres (yellow gross, special stain needed), perichondrium. Fibrocartilage = type I collagen bundles visible in H&E, NO perichondrium. Locations: Epiglottis → always elastic; menisci → always fibrocartilage; articular surfaces → always hyaline.

Incorrect. Hyaline cartilage has type II collagen but no visible elastic fibres and appears glassy/homogeneous. Fibrocartilage has dense type I collagen bundles and NO perichondrium. Elastic cartilage is identified by elastic fibres + perichondrium.

Correct! The nucleus pulposus is the remnant of the embryonic notochord. It contains a semi-fluid gel rich in proteoglycans (chondroitin sulphate and keratan sulphate) and type II collagen — functionally similar to fibrocartilage but with very high water content in youth. It is enclosed by the annulus fibrosus (fibrocartilage with type I collagen). With age and dehydration, the nucleus becomes fibrocartilaginous and prone to herniation.

Intervertebral disc anatomy: Nucleus pulposus (centre — notochordal remnant, type II collagen + proteoglycans, high water content in youth) + Annulus fibrosus (outer fibrocartilaginous ring — type I collagen, obliquely arranged). Disc prolapse = nucleus herniates through annulus → nerve root compression.

Incorrect. The annulus fibrosus (outer ring) is fibrocartilage with type I collagen. The nucleus pulposus is a proteoglycan-rich notochordal remnant with type II collagen. It is distinct from dense fibrous tissue or elastic cartilage.

Correct! Holocrine secretion involves the total disintegration of the secretory cell to form the secretion. The cell accumulates lipid (sebum precursors), and when fully mature, the whole cell ruptures. New secretory cells are continuously produced by mitosis at the periphery of the gland.

Secretion modes: (1) Merocrine = exocytosis, cell intact — pancreatic acini, most sweat glands, salivary glands. (2) Apocrine = apical blebbing — axillary/apocrine sweat glands, mammary glands (fat secretion). (3) Holocrine = whole cell destruction — sebaceous glands only.

Incorrect. Merocrine/eccrine secretion uses exocytosis with intact cell membrane (most glands). Apocrine secretion buds off the apical cytoplasm with the secretion (axillary glands, mammary glands). Endocrine glands secrete into blood, not via ducts.