B2.3- Cell specialisation

Unspecialised cells

- Cells that have not yet developed into one particular type of cell

- Exist in zygote and morula stages of fertilization

production of specialised cells

blastocyst are one of the first stages where cells get specialized because of morphogens that exist in this stage.

What are morphogens?

chemicals in the cell produced in the blastocyst.

- the concentration gradient of morphogens determines the function of cells, and what type of cell it will develop to (mucle, fat, etc.)

-it does this by triggering gene expression.

Types of stem cells

totipotent: embryonic. can differentiate into any type of cell type. Can give rise to a complete organism. found until blastocyst stage.

pluripotent: embryonic and iPSC's. differentiate into all body cells, but cannot give rise to a whole organism. Differentiate into any of three 'germ' layers (no placenta). found until fetus stage.

multipotent: adult stem cells. Can differentiate into a few closely related types of body cell.

unipotent: Can only differentiate into their associated cell type.

properties of stem cells

Divide and renew themselves over a long time.

Potency: The ability to differentiate into different cells.

Unspecialized: no specific functions.

stem cell niche

The microenvironment within the organism in which the stem cells exist and receive their instructions.

Function of stem niches

supports stem cells by maintaining their self-renewal, regulating differentiation, protecting them from damage, and balancing their proliferation to ensure proper tissue repair and homeostasis.

interactions within stem cell niche

- cell-to-cell interactions

- interactions with the fluid outside of the cells (extracellular matrix)

-signalling: can activate, or prevent genes from transcribing

location of stem cell niches

The stem cell niches in humans that have been studied most are those that make blood, skin, intestine, brain and muscle cells.

Example of stem cell niches

1. Bone marrow stem cells: can differentiate into any type of blood cell. Multipotent. Found in bone marrow.

2. Hair follicle: Exist in epidermis. Multipotent. Hair regeneration depends on the activation of hari follicle stem cells.

Cell size as an aspect of specialization

The size and structure of cells is linked directly to their function. (eg. egg cells are large and highly specialised so that they contain all the nutrient materials needed for the early development. The sperm on the other hand does not need such nutritional content and so remains small.)