HE Lec 1

Lecture Overview

  • Title: The Cell

  • Copyright: 2011, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chapter 7 Outline

  • The Cell

    • Cell membrane and cytoplasm

    • Organelles

    • Inclusions

    • Cell Division

    • Extracellular materials

    • Intercellular junctions

Histology

  • Definition: Study of microscopic structure and function of cells and associated tissues.

  • Synonymous term: Microanatomy

Anatomy of the Cell

  • The smallest living unit in the body is the cell, which can perform necessary functions independently.

Tissue Formation

  • Cell grouping: Cells with similar characteristics form a tissue.

  • Tissue bonding: Various tissue types bond to form organs.

  • Organ functions: Organs can function together as a system.

Body Components

  • Cell: Smallest living unit (e.g., epithelial cell, neuron, myofiber).

  • Tissue: Collection of specialized cells (e.g., epithelium, nervous tissue).

  • Organ: Independent part formed from tissues (e.g., skin, brain).

  • System: Organs functioning together (e.g., central nervous system).

Cellular Division

  • Mitosis: Process of cellular division that produces two identical daughter cells.

  • Cellular division is crucial for cell replacement and tissue maintenance.

Interphase and Mitosis

  • Interphase precedes mitosis; during this phase, DNA is replicated.

Exocytosis and Endocytosis

  • Exocytosis: Active transport of materials out of the cell.

  • Endocytosis: Uptake of materials into the cell from the extracellular environment.

  • Phagocytosis: A form of endocytosis where cells engulf solid waste/foreign material.

Cell Membrane and Cytoplasm

  • Cell membrane (plasma membrane): Encloses the cell.

  • Cytoplasm: Contains structures and cavities (vacuoles); includes cytoskeleton.

Organelles

  • Definition: Specialized structures within the cell that are metabolically active.

  • Nucleus: Largest organelle, contains DNA (chromatin). Highly visible under microscopy.

  • Chromatin: Forms visible chromosomes during cell division.

  • Nuclear envelope: Double-layered membrane surrounding the nucleus.

  • Nucleolus: Prominent part within the nucleus, plays a key role in ribosome synthesis.

  • Mitochondria: Most numerous organelles related to energy conversion.

  • Ribosomes: The organelles responsible for protein synthesis; formed in the nucleolus.

Endoplasmic Reticulum (ER)

  • Classification: Smooth ER (lacks ribosomes) and Rough ER (has ribosomes).

  • Functional Role: Modifies newly synthesized proteins; transfers them to the Golgi complex for further processing.

Golgi Complex and Lysosomes

  • Golgi Complex: Packages and transports proteins modified by the ER.

  • Lysosomes: Produced by the Golgi; function in intracellular and extracellular digestion.

Centrosomes and Projections

  • Centrosome: Dense organelle containing centrioles, crucial for cell division.

  • Cytoskeleton: Provides structural support; allows movement of substances within the cell.

  • Cilia and Flagella: Projections; cilia are shorter and numerous, while flagella are longer and fewer.

Inclusions in Cells

  • Inclusions: Metabolically inert substances found transiently within the cell.

Cell Division (Mitosis)

  • Process: Involves many organelles, critical for tissue growth and replacement.

Extracellular Materials

  • Definition: Surround cells in tissue; includes tissue fluid and intercellular substance.

  • Tissue fluid: Provides a medium for transportation and chemical reactions.

  • Intercellular substance (ground substance): Fills the spaces between cells, shapeless and transparent.

Intercellular Junctions

  • Definition: Mechanical attachments between cells and adjacent surfaces.

  • Desmosome: Junction likened to a “spot weld”; important in the skin.

  • Hemidesmosome: Attachment of a cell to a noncellular surface, providing stability in tissues.

difference between desmosome and hemidesosome?

The primary difference between a desmosome and a hemidesmosome lies in their function and structure; while desmosomes connect adjacent cells to each other, providing tensile strength, hemidesmosomes anchor cells to the extracellular matrix, ensuring tissue integrity and stability.

what is extracellular matrix?