Tissues

Types of tissues

Types of Tissues

There are 4 types of tissues:

• Epithelial tissue

• Connective tissue

• Muscle tissue

• Nervous tissue

Epithelial Tissue

Sheets of cells (epithelium) that….

• Cover surfaces

• Line cavities & passageways

• Form Glands

E.g. skin, digestive tract, sweat glands

Connective Tissue

• Connects the cells and organs of the body

• Provides support and protection

E.g. bones, cartilage, blood, adipose tissue.

Muscle Tissue

Responds to stimulation and contracts to provide movement. There are 3 types of muscle tissue:

• Skeletal muscle (voluntary)

• Smooth muscle (involuntary)

• Cardiac muscle (involuntary)

Nervous Tissue

Responds to stimulation to allow the movement of nerve impulses that communicate with different regions of the body.

E.g. brain, spinal cord, nerves

Totipotent

First embryonic cells that can divide, differentiate and develop into any type of cell in the organism.

The Major Cell Lineages

There are 3 major cell lineages that are established within the embryo. These lineages form into distinct germ layers that give rise to all the tissues and organs of the human body:

• Ectoderm = outer layer

• Mesoderm = middle layer

• Endoderm = inner layer

Germ Layer: Ectoderm

The ectoderm gives rise to:

• Epidermis (skin)

• Nervous System

Germ Layer: Mesoderm

The mesoderm gives rise to:

• Muscles

• Bones

• Connective tissue

• blood

• heart

• kidneys

Germ Layer: Endoderm

The endoderm gives rise to:

• Lining of GI tract

• Respiratory tract

• Glands (e.g. pancreas, liver)

Memory Aid: Germ Layers

🧠 Ecto = external (skin, brain)

• Nervous Tissue

💪 Meso = movement (muscle, bone, blood)

• Connective and muscle tissue

🍽 Endo = inner linings (gut, glands)

Epithelial tissue originates in all 3 layers

Tissue Membrane

A thin layer/ sheet of cells that cover the…

• Outer body (e.g. skin)

• Organs (e.g. pericardium)

• Internal passageways that lead to the exterior of the body (e.g. mucosa of stomach)

• lining of moveable joint cavities

Types of Tissue Membranes

There are two basic types:

• Connective tissue membranes

• Epithelial membranes

Connective Tissue Membranes

Formed from connective tissue, these membranes:

• Encapsulate organs

• Line our movable joints

Connective Tissue Membranes: Synovial Membrane

Type of connective tissue membrane that:

• lines the cavity of a freely movable joint (e.g. surrounds the joints of the shoulder, elbow and knee.)

  Does this by producing a lubricant called synovial fluid

Formation of Synovial Fluid

1) Fibroblasts in the inner layer of the membrane release hyaluronan into the joint cavity.

2) The Hyaluronan traps available water to form the synovial fluid

Function of Synovial fluid

A natural lubricant that:

• Allows the bones of a joint to move freely with minimal friction

• Readily exchanges water & nutrients with blood

The epithelial membrane

Made of epithelium attached to a layer of connective tissue (e.g. skin). Epithelial membranes include:

• Mucous membranes

• Serous membranes

• Cutaneous membrane (skin)

Epithelial membrane: Mucous membrane Composition

A composite of connective & epithelial tissues.

• The epithelial exocrine glands produces mucus, which covers the epithelial layer.

• The connective tissue beneath the epithelial tissue, called the lamina propria, helps support the fragile epithelial layer.

Epithelial membrane: Mucous membrane Function

The epithelial mucous membrane lines the

• body cavities & hollow passageways that open to an external environment.

• This includes the digestive, respiratory, excretory & reproductive tracts.

Epithelial membrane: Serous membrane Composition

Composed of mesothelium that is supported by connective tissue.

• Mesothelium lines the inside

• Connective tissue lines the outside

Epithelial membrane: Serous membrane Function

The serous membranes:

• Line the coelomic cavities

• Cover the organs within the coelomic cavities

• Secrete serous fluid from the thin squamous mesothelium to lubricate the membrane & reduce abrasion and friction between organs.

Epithelial membrane: Cutaneous Membrane Composition

The cutaneous membrane (skin) is a:

• Stratified squamous epithelial membrane resting on top of connective tissue.

• The surface exposed to the external environment is covered with dead keratinized cells

Epithelial membrane: Cutaneous Membrane Function

The apical surface covered in dead keratinized cells:

• protect the body from desiccation (drying out) & pathogens.