Tissues & Membranes

Tissue

• Group of cells that have similar structure and that function together as a unit.

Intercellular Matrix

• Intercellular matrix (nonliving) fills the spaces between the cells.

  • Abundant in some tissues and minimal in others

  • May contain special substances like salts and fibers and are unique to a specific tissue and gives distinctive characteristics.

Four Main Body Tissues

• Epithelial

• Connective

• Muscle

• Nervous

Epithelial Tissue

• Form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands.

• Functions: Protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.

• Tightly packed together - little intercellular matrix. The cells have one free surface that’s not in contact with other cells.

• Cells are attached to underlying connective tissue by non-cellular basement membrane

  • Membrane is a mix of carbs and proteins secreted by epithelial and connective tissue cells.

Types of Epithelium

• Simple squamous

  • Thin, single layer of flat cells that line various surfaces in the body + helps the movement of gases between lungs and blood vessels.

• Simple cuboidal

  • In glandular tissue and the kidney tubules

• Simple columnar

  • Lines the stomach and intestines

• Transitional

  • AKA urothelium + specialized type of stratified epithelium that lines the urinary tract: bladder, ureters, and urethra.

• Stratified squamous

  • Protection against mechanical stress, abrasion, and microbial invasion

• Stratified cuboidal

  • Protection in large exocrine glads, and helps with secretion

• Pseudo-stratified columnar

  • Lines portions of the respiratory tract and some of the tubes of the male reproductive tract

• Transitional

  • Can be distended or stretched

• Glandular

  • Specialized to produce and secrete substances

Connective Tissue

• Functions

  • Bind structures together

  • Forms framework and support for organs and that body as a whole

  • Store fat

  • Transport substances

  • Protect against disease

  • Help repair tissue damage

• Characteristics

  • Abundance of intercellular matrix with relatively few cells

  • Cells reproduce but not as rapidly as epithelial cells

  • Most have good blood supply but some don’t

Connective Tissue Cell Types

• Fibroblast

• Macrophage

• Mast Cell

• Includes:

  • Loose connective tissue

  • Adipose tissue

  • Dense fibrous connective tissue

  • Elastic connective tissue

  • Cartilage

  • Osseous tissue (bone)

  • Blood

Muscle Tissue

• Composed of cells that have the special ability to shorten or contract to produce movement of the body parts

• Tissue is highly cellular and is well supplied with blood vessels

• Cells are long and slender

  • Sometimes called muscle fibers

  • Usually arranged in bundles or layers surrounded by connective tissue

• Actin and myosin are contractile proteins in muscle tissue

• Muscle tissue can be categorized into:

  • Skeletal muscle tissue

  • Smooth muscle tissue

  • Cardiac muscle tissue

Muscle Tissue Types

• Skeletal muscle fibers

  • Cylindrical

  • Multinucleated

  • Striated

  • Under voluntary control

• Smooth muscle cells

  • Spindle shaped

  • Single centrally located nucleus

  • Lacks striations

• Cardiac muscle

  • Branching fibers

  • One nucleus per cell

  • Striations

  • Intercalated disks

  • Contraction is not under voluntary control

Nervous Tissue

• Found in the brain, spinal cord and nerves

• Responsible for coordinating and controlling body activities

  • Stimulates muscle contraction

  • Creates awareness of environment

  • Plays major role in emotions, memory, and reasoning

• Cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses

  • Neurons (nerve cells) generate and conduct impulses

• Three principle parts:

  • Dendrites

  • Cell body

  • Axon

• Cell body is the main part of the cell and carries general functions

Nervous Tissue Cells

• Three principle parts:

  • Dendrites

    • Extensions or processes of cytoplasm that carry impulses to cell body

  • Cell body

    • Main part of the cell and carries general functions

  • Axon

    • Extension or process that carries impulses away from the cell body

• Cells that do not transmit impulses but support the activities of neurons:

  • Glial cells (neuroglial cells) Together the neuroglia

  • Supporting or glia cells bind neurons together and insulate neurons

  • Some are phagocytic and protect against bacterial invasion

  • Others provide nutrients by binding blood vessels to neurons

Membranes

• Body membranes are thin sheets of tissue that:

  • Cover the body

  • Line body cavities

  • Cover organs within the cavities in hollow organs

• Can be categorized into epithelial and connective tissue membrane

Types of Membranes

• Epithelial Membranes

• Mucous Membranes

• Serous Membranes

• Connective Tissue Membranes

• Synovial Membranes

• Meninges

Epithelial Membranes

• Consist of epithelial tissue and the connective tissue that it is attached to.

• Two main types of epithelial membranes are the mucous membranes and serous membranes

Mucous Membranes

• Epithelial membranes that consist of epithelial tissue attached to underlying loose connective tissue

• Membranes (mucosae) line the body cavities that open to the outside

• Digestive tract is lined with this

• E.g. respiratory, excretory, and reproductive tracts

Serous Membranes

• Line body cavities that do not open directly to the outside

• Cover organs located in those cavities

• Covered by a thing layer of serous fluid secreted by the epithelium

  • Lubricates the membrane and reduces friction and abrasion when organs in the thoracic or abdominopelvic cavity move against each other or the cavity wall

• Have special names given according to location

  • E.g. Lining the thoracic cavity and covers lungs is called pleura

Connective Tissue Membranes

• Contain only connective tissue

• Synovial membranes and meanings belong to this category

Synovial Membranes

• Connective tissue membranes that line the cavities of the freely movable joints such as the shoulder elbow and knee

• Line cavities that do not open to the outside

• Do not have a layer of epithelium

• Secrete synovial fluid to joint cavities to lubricate the cartilage on ends of bones so they can move freely w/o friction

Meninges

• Connective tissue covering on the brain and spinal cord

• Is within the dorsal cavity

• Provide protection