Biology: Tissue Types

Epithelial Tissue: forms the lining of organs, glands, and other body surfaces; functions in absorption, secretion, and protection
- Characteristics:
  - avascular (no blood vessels)
  - tightly packed cells
  - supported by basement membrane
- Types:
  - Squamous (flat)
  - Cuboidal (cube-shaped)
  - Columnar (column-shaped)
  - Transitional (variable shape)
Connective Tissue: provides support, structure, and connectivity to the body; functions in storage, transport, and protection
- Characteristics:
  - abundant extracellular matrix
  - varied cell types
  - richly vascularized
- Types:
  - Loose connective tissue (e.g., areolar, adipose)
  - Dense connective tissue (e.g., tendons, ligaments)
  - Specialized connective tissue (e.g., cartilage, bone)
Muscle Tissue: responsible for movement, contraction, and relaxation; functions in locomotion, maintenance of posture, and regulation of body temperature
- Characteristics:
  - ability to contract and relax
  - multinucleated cells
  - richly vascularized
- Types:
  - Skeletal muscle (voluntary)
  - Smooth muscle (involuntary)
  - Cardiac muscle (heart)
Nervous Tissue: responsible for transmitting and processing information; functions in control and coordination of body functions
- Characteristics:
  - specialized cells (neurons, glial cells)
  - ability to transmit electrical signals
  - richly vascularized
- Types:
  - Central nervous system (CNS)
  - Peripheral nervous system (PNS)

Cell Adhesion Molecules (CAMs): proteins that facilitate cell-to-cell and cell-to-extracellular matrix interactions
- Types:
  - Transmembrane CAMs (e.g., integrins, cadherins)
  - Glycoprotein CAMs (e.g., selectins, immunoglobulins)
- Functions:
  - cell migration and adhesion
  - tissue development and organization
  - immune responses
Adherens Junctions: structures that provide strong mechanical adhesion between cells
- Characteristics:
  - formed by transmembrane proteins (e.g., E-cadherin)
  - linked to actin cytoskeleton
- Functions:
  - maintain tissue architecture
  - regulate cell migration and proliferation
Tight Junctions: structures that form a impermeable barrier between cells
- Characteristics:
  - formed by transmembrane proteins (e.g., occludin, claudin)
  - linked to actin cytoskeleton
- Functions:
  - regulate paracellular transport
  - maintain epithelial polarity

Epithelial tissue forms the lining of organs, glands, and other body surfaces, and functions in absorption, secretion, and protection.
Characteristics of epithelial tissue include being avascular, having tightly packed cells, and being supported by a basement membrane.
There are four main types of epithelial tissue: squamous, cuboidal, columnar, and transitional.
Connective tissue provides support, structure, and connectivity to the body, and functions in storage, transport, and protection.
Characteristics of connective tissue include having an abundant extracellular matrix, varied cell types, and being richly vascularized.
There are three main types of connective tissue: loose, dense, and specialized.
Muscle tissue is responsible for movement, contraction, and relaxation, and functions in locomotion, maintenance of posture, and regulation of body temperature.
Characteristics of muscle tissue include the ability to contract and relax, having multinucleated cells, and being richly vascularized.
There are three main types of muscle tissue: skeletal, smooth, and cardiac.
Nervous tissue is responsible for transmitting and processing information, and functions in control and coordination of body functions.
Characteristics of nervous tissue include having specialized cells (neurons and glial cells), the ability to transmit electrical signals, and being richly vascularized.
There are two main types of nervous tissue: central nervous system (CNS) and peripheral nervous system (PNS).

Cell adhesion molecules (CAMs) are proteins that facilitate cell-to-cell and cell-to-extracellular matrix interactions.
There are two main types of CAMs: transmembrane CAMs (such as integrins and cadherins) and glycoprotein CAMs (such as selectins and immunoglobulins).
CAMs function in cell migration and adhesion, tissue development and organization, and immune responses.
Adherens junctions are structures that provide strong mechanical adhesion between cells.
Characteristics of adherens junctions include being formed by transmembrane proteins (such as E-cadherin), being linked to the actin cytoskeleton, and functioning to maintain tissue architecture and regulate cell migration and proliferation.
Tight junctions are structures that form an impermeable barrier between cells.
Characteristics of tight junctions include being formed by transmembrane proteins (such as occludin and claudin), being linked to the actin cytoskeleton, and functioning to regulate paracellular transport and maintain epithelial polarity.