4 - Basic tissues

What are the 4 basic tissues?

• Epithelial

• Connective

• Nervous

• Muscle

What does epithelial tissue do?

• Covers surfaces

• Line cavities and tubes

• Form glands

What are the important characteristics of epithelial tissue?

• Attachment - sticks to things, maintains integrity of barriers

• Avascularity - no blood supply but nutrients from diffusion

• Regeneration - Maintains integrity of barrier by producing new cells

• Polarity - Apical, head of cell. Basal, tail of cell

What is the basic structure of epithelial tissue?

Closely packed cells supported by a basement membrane

Most epithelial cells supported by connective tissues underneath

How are epithelia classified?

• Number of cell layer

  • Simple - one layer

  • Stratified - two or more layers

• Shape

  • Squamous (flat)

  • Cuboidal (cube)

  • Columnar (rectangular)

Describe simple squamous epithelia, their major function and location

• One layer of flat cells, oval shaped nuclei

• Major function - facilitates exchange of nutrients and gases

• Location - blood vessels, alveoli

Describe Non keratinised stratified squamous, major location and function

• Flat surface cells with oval shaped nuclei

• Many layers

• Major function - protection barrier (from mechanical stress)

• Location - oral cavity, oesophegus

Describe keratinised stratified squamous, major function and location

Flat surface cells with oval shaped nuclei

Many layers

Keratin

Major function - protection, barrier (tough and waterproof)

Location - skin

Describe simple cuboidal epithelium, major function and location

Square cells with round nuclei

One layer

Major function - absorption and secretion

Location - glands, kidney tubules

Describe simple columnar epithelium, major location and function

Tall cells with oval, basally located nuclei

One layer (with microvilli, cytoplasmic extension)

Major function - absorption and secretion

Location -GI tract

Surface modifications - microvilli

describe psuedostratified ciliated columnar epithelium with goblet cells (respiratory)

Tall cells

Appears stratified as some cells don’t reach free surface. All cells touch basement membrane (but appears falsely stratified)

Modifications - cilia and goblet cells (produce mucus)

Functions - mucociliary escalator

Location - trachea and large respiratory airways

What are intercellular junctions?

Specialised areas of cell membrane that bind one cell to another

What are some examples of intercellular junctions?

Desmosomes

Hemidesmosomes

Tight junctions

Gap junctions

What are desmosomes?

Very strong connections that join adjacent cells resist stretching and twisting of epithelial barrier

What are Hemidesmosomes?

Attaches cells to basement membrane anchoring the basal end of the cell to the basement membrane

What are Tight junctions?

Located near the apical side of the cell

Interlocking proteins joining the two cells together

Stops things like water and solutes passing in-between cells

Gap junctions

Connexons (interlocking proteins)

Central pore which allows movement of small molecules and ions between cells

Found in cardiac muscle

What are the functions of connective tissue?

Forms a structural framework from the body

Supports, surrounds and interconnects other tissue types

Protects delicate organs

Transports fluid and dissolved tissues

Stores energy reserves

Defends body from microorganisms

How is connective tissue structured?

Consists of cells within an extracellular matrix

What are the cells in connective tissues?

Fibroblasts (main cell type, synthesises ECM)

Others; adipocytes, macrophages and mast cells

What does the extracellular matrix consist of?

Ground substance

tissue fluid

Fibres; collagen; reticular and elastic

What are the specialised connective tissues and their consistencies?

Blood - extracellular fluid is watery

Bone - extracellular fluid is tough

Cartilage - extracellular fluid is jelly like

What are the 3 connective tissue propers?

Loose (areolar) connective tissue

Dense irregular connective tissue

Dense regular connective tissue

What does Loose connective tissue contain and where is it found?

Lots of ground substance

Few fibres (collagen and elastic)

Variety of cells

• Fibroblasts

• apidocytes

• macrophages

Found under the epithelium that covers and lines the body surfaces

What does Dense irregular connective tissue contain and where is it found?

Contains little ground substance

Many collagen fibre bundles arranged haphazardly

Few cells (mainly fibroblasts)

• Resists excessive stretching and distension

Found in the dermis

What does dense regular connective tissue contain and where is it found?

contains little ground substance

Mainly densely packed bundles of collagen fibres arranged in parallel rows

Few cells (mainly fibroblasts)

Found in tendons and ligaments

What does muscle tissue do and what are the 3 types?

• Produces movement and is specialised for contractions

Skeletal, cardiac, smooth

What are the similarities in the 3 muscle tissues?

Elongated parallel to axis of contraction

Numerous mitchondria

Contractile elements (actin and myosin)

What does skeletal muscle do?

Moves and stabilises skeleton

Forms sphincters in digestive and urinary tracts

Involved in respiration

Innervated by somatic nervous system

What does skeletal muscle look like under a microscope ?

Long cylindrical fibres

Straited (striped)

Multinucleated

Where is smooth muscle located and what does it do?

Located in walls of organs, blood vessels and airways

GI movement (contract and propel forwards)

Alters diameter of airways and blood vessels

What does smooth muscle look like under a microscope?

Short, uniform cells

Non-striated

Single, centrally located nucleus

Innervated by autonomic nervous system

Where is the cardiac muscle found and what does it do?

Found in heart wall

Helps to circulate blood and regulate pressure

What does cardiac muscle look like under a microscope?

Branched muscle fibres

Striated

Single, centrally located nucleus

Innervated by autonomic nervous system