Topic 2 - cell, tissues and organs Flashcards
The human body involves five levels of structural organisation:
Atoms and molecules Cells Tissues Organs Systems
The human body involves five levels of structural organisation:
Atoms and molecules Cells Tissues Organs Systems
Atoms and molecules
Atoms and molecules are the lowest level of organisational complexity in the body.
Cells
Cells are the smallest units that show characteristics of life.
Tissues
Tissues are a group of similar cells that perform a certain function.
Organs
Organs are tissues grouped into structurally and functionally integrated units.
Systems
Systems are a group of organs that work together to perform specific functions.
The tissues of the body are classified into four main types:
Epithelial
Connective
Muscular
Nervous.
Tissue Types
There may be various sub-tissues within each of the primary tissues.
In tissues the simplest combination is called a membrane, or a sheet of tissues which cover or line the body surface or divide organs into parts. Examples include the mucous membrane which lines body cavities. Tissues combine to form organs.
An organ is a part of the body which performs a definite function. The final units of organization in the body are called systems. A system is a group of organs each of which contributes its share to the function of the body as a whole.
Epithelial Tissue
This tissue covers the body surface and forms the lining for most internal cavities. The major function of epithelial tissue includes protection, secretion, absorption, and filtration.
Cells of the epithelial tissue have different shapes.
Cells can be thin, flat to cubic to elongated.
The skin is an organ made up of epithelial tissue which protects the body from dirt, dust, bacteria and other microbes that may be harmful.
Connective tissue
Connective tissue is the most abundant and the most widely distributed of the tissues. Connective tissues perform a variety of functions including support and protection.
The following tissues are found in the human body, ordinary loose connective tissue, fat tissue, dense fibrous tissue, cartilage, bone, blood, and lymph, which are all considered connective tissue.
Nervous Tissue
Nerve tissue is composed of specialized cells which not only receive stimuli but also conduct impulses to and from all parts of the body. Nerve cells or neurons are long and string-like.
Muscle Tissue
There are three types of muscle tissue: skeletal, smooth, and cardiac.
Skeletal muscle
skeletal muscle is a voluntary type of muscle tissue that is used in the contraction of skeletal parts.
Smooth muscle
Smooth muscle is found in the walls of internal organs and blood vessels. It is an involuntary type.
