Question

1. Why the hypodermis layer is not part of the skin ?

2. Why fibrocartilage is the toughest kind of cartilage. And received a lot of mechanical stress?

3. Why ribosomes/ribosomal subunits are free in the cytoplasm?

4. Why sens on the axis (c2) forms a pivot with the atlas (c1) that allows you to nod a “no”

Answer 1

1.Why the hypodermis is not part of the skin?

Skin is composed of two main layers

• Epidermis
• Dermis

Below (hypo) the dermis lies the layer called hypodermis or subcutaneous tissue.

Hypodermis is made up of fatty tisse and connective tissue which actually has a cushioning and insulating effect (maintains body temperature).

Hypodermis layer just helps to connect the skin to the bones and musles and also supplies blood vessels and nerves to the dermis which in turn provides nutrition to the epidermis which do not contain blood vessels.

Hypodermis contains SWAT (Subcutaneous White Adipose Tissue) whose origin is different from DWAT (Dermal White Adipose Tissue). DWAT is found in dermis.

2. Why fibrocartilage is the toughest kind of cartilage. And received a lot of mechanical stress?

Cartilage is of three main types

• Hyaline
• Elastic
• Fibro

Hyaline and elastic cartilage is composed of type II collagen fibers,where as fibrocartilage is made up of type I and type II collagen fibers.

Fibrocartilage also contains alternate, parallel rows of chondrocytes in between collagen fibres. Chondrocytes increases the tensile strength of fibrocollagen.

The presence of type I collagen makes fibrocartilage strong and tensile.

As fibrocartilage is stron and tensile it can receive a lot of mechanical stress.

3.Why ribosomes/ribosomal subunits are free in the cytoplasm?

Ribosomes or ribosomal subunits are found attached to the endoplaspic reticulum or found freely floating in the cytoplasm called as detached ribosomes.

The free ribosomes or ribosomal subunits cannot move into the nucleus or to the other organelles.

The floating ribosomes or ribosomal subunits in the cytoplasm is used to synthesise proteins to be secreted directly into the cytoplasm.

The floating ribosomes or ribosomal subunits are mostly involved in cellular metaboloism and in synthesising protein enzymes required to release energy from glucose.

Where as attached ribosomes help in the synthesis of proteins that are targeted for the functions outside the cell.

4.Why dens on the axis (c2) forms a pivot with the atlas (c1) that allows you to nod a “no”

The dens is also called the odentoid process or peg and arises from the second cervical vertebrae C2,the axis. Dens is a bony projection from C2 which fits into the concave depression on the first cervical vertebrae, the atlas.

Dens acts as the pivot point in the neck and the articulation between CI and C2 helps us to nod our head.