Human Cell Biology: Structure, Function, Tissues, and Diseases
Human Cells: An Introduction
Human cells: The cell is the basic unit of all living beings. The human body is composed of many cells. These are eukaryotic cells, meaning they contain a nucleus. The nucleus houses DNA and is enclosed by a double membrane called the nuclear membrane. During cell division, the nuclear membrane fragments, and the genetic material compacts into chromosomes.
Organelles in Human Cells and Their Functions
The Nucleus:
Controls all cell functions through DNA.
Ribosomes:
Composed of two subunits, they are involved in protein synthesis, controlled by DNA.
Vacuoles:
Membrane-bound vesicles that store various materials, such as nutrient reserves.
Mitochondria:
The site of cellular respiration, where nutrients and oxygen are used to produce energy.
Centrioles:
Small, cylindrical organelles that direct chromosome separation during cell division.
Cytoskeleton:
A network of protein strands within the cytoplasm that provides cell shape and support.
Endoplasmic Reticulum:
A network of membranous sacs, some of which are covered with ribosomes.
Golgi Apparatus:
Receives substances from the endoplasmic reticulum and packages them into vesicles for transport outside the cell.
Lysosomes:
Small vesicles filled with digestive enzymes.
Different Cells and Tissues
The human body is a multicellular organism composed of specialized eukaryotic cells. These cells are organized into four main tissue types: epithelial, muscular, nervous, and connective. Each tissue type has distinct cells and functions.
Types of Tissue
Epithelial Tissues:
Protective tissues made of closely packed cells that cover external and internal surfaces. They also form glands that secrete substances.
Muscular Tissue:
Composed of contractile muscle fibers responsible for movement.
Nervous Tissue:
Composed of neurons that capture and respond to stimuli, controlling the body’s activities.
Connective Tissue:
Cells separated by an extracellular matrix. Its consistency varies from solid to liquid.
Connective tissue: Fills organs, such as ligaments and tendons.
Bone tissue: Hard and tough due to its mineralized matrix, forming the skeleton.
Cartilaginous tissue: Flexible and resilient, found in cartilage and joints.
Adipose tissue: Fat-filled cells that provide thermal insulation, energy storage, and protection from shocks.
Blood tissue: The matrix is a liquid called plasma, containing red blood cells (for gas transport) and white blood cells (for defense).
Disease
Disease is any decline in health.
Types of Disease
Infectious Diseases:
Can be transmitted from one person to another and are caused by pathogens.
Non-Infectious Diseases:
Cannot be transmitted and are related to internal or external factors.
Prevention
Disease prevention involves applying measures to reduce risk factors.
Pathogens
Pathogens include viruses, bacteria, protozoa, and other organisms that can enter the body, grow, and cause infectious diseases.
Transmission of Pathogens
The transmission of infectious diseases involves a source of infection and a mechanism of transmission, which can be direct or indirect.
Virulence
Virulence is the capacity of a pathogen to cause disease.
Risk of Infection and Its Prevention
Risk:
Increases for people living in environments that favor the presence of pathogens.
Prevention:
Avoid contact with infected individuals and control the health of food and water.