histo- practice questions

Question 1

Mention 2 histological features in transitional epithelium (uroepithelium) that prevent reabsorption of urine.

Answer 1

1. Umbrella cells with tight junctions
   - sealed tightly together using tight junctions that create a waterproof barrier to prevent urine from passing between cells
2. multiple stratified epithelium layers
   - thickness provides a strong barrier so that substances like urea cant easily damage or pass easily

Question 2

Briefly explain structure of desmosomes.

Answer 2

strong cell-to-cell junctions that hold adjacent cells tightly together, especially in tissues that face a lot of stress, like the skin, heart, and epithelial tissues

structure:
1. Intermediate filaments: keratin filaments attach to the desmosomal plaque
- act like anchors, spreading mechanical stress across the cell

2. Cadherin proteins: transmembrane proteins that bind to matching cadherins to form strong adhesion b/w cells
3. Desmosomal Plaques (cytoplasmic plaques): dense protein plates on inner surface of cell membrane of both adjacent cells

Question 3

Classify simple epithelia giving one example of each.

Answer 3

1. simple squamous: single layer of flat, thin cells with a central, flattened nucleus
   - function: diffusion & filtration
   - ex. lining of blood vessels, alveoli of lungs
2. simple cuboidal: single layer of cube-shaped cells with round, central nuclei
   - function: secretion & absorption
   - *ex. kidney tubules
3. simple columnar: single layer of tall, column-like cells with oval nuclei usually at the base
   - function: absorption & secretion of mucus & enzymes
   - ex. lining of small intestine
4. pseudostratified columnar: appears to have multiple layers because the nuclei are at different levels, but all cells touch the basement membrane, so it’s still simple
   - function: secretion & movement of mucus
   -* ex. lining of trachea*

Question 4

How will you differentiate a diagram of fibrocartilage from a diagram of hyaline cartilage?

Answer 4

fibrocartilage:
- many thick collagen fibers (Type I)
- fibers are clearly visible
- chondrocytes (cartilage cells) arranged in rows/lines
- perichondrium is absent

hyaline cartilage:
- fine collagen fibers (Type II)
- matrix looks smooth and glassy
- chondrocytes in small groups/singly lacunae
- perichondrium is present

Question 5

Name the 3 types of protein fibers that make up the cytoskeleton, giving one example of each type.

Answer 5

1. microfilaments (actin filaments): maintain cell shape, help with cell movement, involved in muscle contraction & cytokinesis
   ex. actin filaments in muscle cells
2. intermediate filaments: provide mechanical strength, stabilize cell shape, and help anchor organelles in place
   - ex. keratin in skin cells
3. microtubules: form mitotic spindle during cell division, serve as tracks for transport of organelles, has protein tubulin
   - ex. spindle fibers during mitosis

Question 6

give a brief account of ultra-structure of nuclear envelope.

Answer 6

double membrane:
- outer membrane that is continuous with the rough ER and has ribosomes on its surface
- inner membrane that faces the inside of the nucleus and is supported by the

nuclear lamina: dense, fibrous network beneath the inner membrane that provides mechanical support to the nuclear envelope

nuclear pores: large openings that allow controlled exchange of materials

Question 7

Explain the blood supply of long bone by nutrient artery.

Answer 7

nutrient artery: main source of blood supply to the diaphysis (shaft) of long bone

1. nutrient artery enters through nutrient foramen (small hole usually located on shaft surface)
2. artery travels through compact bone and into medullary cavity (central cavity of bone filled w/ marrow)
3. inside bone, divide into smaller branches that supply bone marrow, the spongy bone, and cortex
4. epiphyses (ends of long bone) are typically supplied by metaphyseal vessels & periosteal vessels not nutrient artery

Question 8

Why are bone infections more common in children?

Answer 8

in children, nutrient artery that supplies the bone has a direct connection to the metaphysis (where the epiphyseal plate or growth plate is located)

• blood vessels in the metaphyseal region are less protected and more prone to infection
• venous drainage is also poorly developed