B2.3 Cell specialisation

What are the properties of stem cells?

• Can divide repeatedly with no limit

• Can remain undifferentiated or specialise

• Found in skin, testes, and other tissues

• Enable growth, repair, and regeneration

Where are stem cell niches in adults?

Bone marrow, skin, liver hair, follicles

What is the role of stem cell niches in adults?

• Provide microenvironment to keep stem cells inactive or trigger activity

• Enable regeneration and tissue repair

What is totipotent?

Form all cell types including embryonic and extra-embryonic

What is pluripotent?

Form many but not all cell types

What is multipotent?

Form limited range of specialised cells

How are sperm optimised in cell size specialisation?

Long and thin for motility

How are eggs optimised in cell size specialisation?

Largest human cell, nutrient reserves

How are RBCs optimised in cell size specialisation?

Biconcave, small volume, large surface area to volume ratio → efficient gas exchange

How are neurons optimised in cell size specialisation?

Long axons for fast transmission

How are muscle fibres optimised in cell size specialisation?

Long, multi-nucleated → strong contraction

What does metabolic rate depend on?

Cell volume

What does exchange rate depend on?

Surface area

What does a low surface area to volume ratio cause?

Slows exchange, causes waste accumulation