Lecture_2__Part_2__Recording_5

Chapter Five: Histology

• Histology is the study of tissues.

• Tissues consist of collections of cells that serve a similar purpose or function.

• Tissues can be made up of the same cell type or multiple cell types working together.

• Multiple tissues form organs in the body.

Cell Estimates

• Various estimates suggest the human body consists of approximately 50 trillion to 75 trillion cells.

• There are roughly 200 different cell types in the human body.

  • Example: Bone has four different types of bone cells.

  • Blood has red blood cells and five different types of white blood cells, with additional developmental stages contributing to their formation.

  • Bone marrow produces cells that generate platelets.

Genetic Information in Cells

• All somatic (non-reproductive) cells in the body share the same genome composed of genes and their variations (alleles).

• Exception includes gametes (sperm and egg), which are haploid and contain only half the number of chromosomes.

Differentiation of Cell Types

• Despite sharing the same genome, cells can exhibit different appearances and functions.

• This differentiation is largely due to gene expression, which determines which genes are turned on or off in different cell types.

• Various stimuli, including signaling pathways, influence gene expression patterns.

Importance of Histology

• Understanding tissues helps in identifying unknown organs or diagnosing diseases based on tissue appearance.

• Recognizing features of healthy versus diseased tissues aids in diagnosing ailments.

Focus of Upcoming Lectures

• Next lectures will explore specific primary tissue types with a focus on epithelial tissues.