What exactly is a tissue?
Cells are the basic structural and functional units, together with extracellular material they
form tissue. To form a tissue cells need to communicate with each other.
Cells can form a specialized tissue by concentrating different organelles and developing
specific cellular activities
Tissue Cells Extracellular Main Functions
Matrix
Nervous Intertwining None Transmission of nerve impulses
elongated
processes
Epithelial Aggregated Small amount Lining of surface or body cavities,
polyhedral glandular section
cells - Covering, lining, and protecting
surfaces (skin)
- Absorption (the intestines)
- Secretion (the epithelial cells of
glands)
- Contractility (myoepithelial cells)
2 types of epithelia:
- Covering or lining epithelia
- Glandular epithelia (Secretory
epithelia & glands)
Muscle Elongated Moderate amount Strong contraction, body movement.
contractile Excitable, responding to stimulation and
cells contracting to provide movement, and
occurs as three major types:
- skeletal (voluntary) muscle
- smooth muscle
- cardiac muscle in the heart
Connective Several Abundant Binds the cells and organs of the body
types of (overvloedig) together and functions in the protection,
fixed and amount support, and integration of all parts of
wandering the body.
cells 3 types:
- Connective tissue proper
- Reticular tissue
- Mucoid tissue
Parenchyma: cells responsible for the main functions of an organ
Stroma: supportive tissue, mostly connective tissue.
, What are the four main types of tissue? (muscle tissue, connective tissue, epithelial tissue,
neuron tissue)
o Epithelial tissue
Structure
Closely aggregated polyhedral cells with very little extracellular substance.
These cells have strong adhesion and form cellular sheets that cover the
surface of the body and line its cavities
The apical, top, side of an epithelial cell faces the inside of a cavity or the
outside of a structure and is usually exposed to fluid or air. The basal,
bottom, side faces the underlying cells.
Epithelial cells are tightly packed, and this lets them act as barriers to the
movement of fluids and potentially harmful microbes. Often, the cells are
joined by specialized junctions that hold them tightly together to reduce
leaks.
Function
- Covering, lining, and protecting surfaces
- Absorption
- Secretion
- Contractility
Subtypes
- Covering epithelia: Cells are
organized in layers that cover
the external surface or line
the cavities of the body
Simple Epithelia: Simple epithelium consists of a single layer of cells. They
are typically where absorption, secretion and filtration occur. The thinness of
the epithelial barrier facilitates these processes.
- Simple Squamous: Flat and in a single layer. This single layer is thin
enough to form a membrane that compounds can move through via
passive diffusion.
- Simple Cuboidal: Single layer cells that are as tall as they are wide.
The important functions of the simple cuboidal epithelium are
secretion and absorption.
- Simple Columnar: Single row of tall, closely packed cells. They have a
high secretory function and possess cellular extensions.
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