Stem Cells along with Specialised Cells

What are stem cells?

Unspecialised cells that can divide and differentiate into specialised cells.

What are the two main properties of stem cells?

Self-renewal and potency.

What is self-renewal in stem cells?

The ability to divide repeatedly while remaining undifferentiated.

What is potency?

The capacity to differentiate into different types of specialised cells.

Where are embryonic stem cells found?

In early embryo tissues up to about 3–5 days after fertilisation (blastocyst).

Are cord blood stem cells embryonic stem cells?

No.

Where are adult stem cells found?

In juvenile and adult tissues such as brain, heart, bone marrow, lungs, skin, and gut.

What is totipotent?

Able to form all cell types of the body.

When are cells totipotent?

In very early embryos (up to about 5 days, morula stage).

What is pluripotent?

Able to form most cell types except embryonic membranes.

Where are pluripotent cells found?

In the blastocyst (early embryo up to about 7 days).

What is multipotent?

Able to form a limited range of cells within a specific lineage.

Where are multipotent stem cells found?

In adult stem cell niches.

What is a stem cell niche?

A specialised tissue environment that maintains stem cells in an undifferentiated state.

What signals regulate stem cell behaviour in niches?

Chemical signals such as growth factors binding to cell surface receptors.

Where are bone marrow stem cell niches found?

In bone marrow, producing blood cells.

What medical use do bone marrow stem cells have?

Used after cancer treatments such as leukemia.

Where are hair follicle stem cells found?

In hair follicles, involved in hair growth and skin regeneration.

Which animals possess pluripotent stem cells in adulthood?

Starfish, salamanders, crabs, and planarians.

What is regeneration?

The ability to replace lost tissues or body parts.

How does cell size relate to specialisation?

Cell size and shape are adapted to the function of the cell.

Why are sperm cells long and narrow?

To reduce resistance and swim efficiently toward the egg.

Why do sperm cells contain many mitochondria?

To supply energy for movement.

Why are egg cells large?

To store large quantities of food reserves.

Why are red blood cells biconcave and flat?

To increase surface area for oxygen exchange and pass through narrow vessels.

Why do red blood cells lack a nucleus?

To maximise space for oxygen transport.

What is the function of white blood cells?

Defence against disease through antibodies or phagocytosis.

Why do white blood cells have a large volume?

To contain rER and Golgi for protein synthesis.

What is the function of motor neurons?

To transmit electrical signals to muscles or glands.

Why are motor neurons long?

To transmit signals over long distances (up to 1 m or more).

Why are muscle cells large and multinucleate?

To generate greater force and contraction length.