LEC.02 Tissues

What is a tissue?

Aggregate of similar cells with a common embryonic origin and similar morphological features. Tend to be organized in an orderly fashion.

What kind of tissues form organs?

Two or more types

What are the four basic types of tissues?

Epithelial, connective, muscle, and nervous

Epithelial Tissue

-Closely packed cells

-Covers internal and external organs

-Forms most glands

Connective Tissue

-Widely spaced cells with extracellular material

-Support and bind together other tissues

Muscle

—

Nervous

—

What are characteristics of Epithelial Tissue?

-Anchored by basement membrane

-Lack blood vessels

-Regeneration

-Surface specialization

Basement Membrane

Noncellular glycoprotein and collagen provide attachment site for epithelium. Anchored to underlying connective tissue

How is Epithelial Tissue classified?

-Number of cell layers (simple or stratified)

-Cell shape (squamous, cuboidal, and columnar)

Glandular Epithelial Tissue

-Functional group of cells whose main function is secretion

-Develop by invagination of epithelium into underlying tissue

What are the three types of Exocrine Glands?

-Merocrine

-Apocrine

-Holocrine

Merocrine

Known for secreting thin, watery substances that can pass through the cell membrane

Apocrine

Top of cell gets pinches off, secretes thicker fluids that holds proteins and fats

Holocrine

Whole cell matures, explodes, and dies. A sebaceous gland

Connective Tissue Characteristics

-Function to provide support and connection

-Widely separated cells with extracellular matrix

-Rich in blood supply

What are the four components of Connective Tissue?

-Cells

-Fluid

-Fibers

-”Ground substances”

What are the different types of ground substance?

-Liquid

-Semisolid

-Solid

What are the different (3) types of Connective Tissue?

-Connective tissue proper

-Supportive connective tissue

-Fluid connective tissue

What are the two types of Connective Tissue Proper?

1) Loose connective tissue

2) Dense connective tissue

What are the three types of 1) Loose Connective Tissue?

-Areolar

-Adipose

-Reticular

What are the two types of Dense Connective Tissue?

-Regular

-Irregular

What do all types of connective tissue contain?

Fibroblasts, which secrete the ground substance and fibers (collagen, elastic, or reticular)

What are the three different fibers in Connective Tissue?

-Collagenous

-Elastic

-Reticular

Collagenous Fibers

Major type composed of protein collagen and is like string (tough and flexible but inelastic)

Elastic Fibers

Thinner than collagenous and composed of protein elastin. Like a rubber band, stretch and recoil

Reticular Fibers

Thins single strands of collagenous fibers, forms a fine meshwork

Areolar Tisse

Shows little specialization. It contains all the cell types and fibers previously described and is distributed in a random, web-like fashion. It fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity.

Areolar tissue underlies most epithelia

Adipose Tissue

Consists mostly of fat storage cells, with little extracellular matrix. A large number of capillaries allow rapid storage and mobilization of lipid molecules

Reticular Tissue

A mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver. Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin reticulus, which means “little net.”

Dense connective tissue contains more ______ fibers than loose connective tissue..

Collagen

What are the three layers of the skin? (superficial to deep)

1) Epidermis

2) Dermis

3) Subcutaneous

Epidermis

Stratified squamous consisting of 4-5 layers of epithelial cells

What are the five layers of the Epidermis? (in order)

1) Stratum basale

2) Stratum spinosum

3) Stratum Granulosum

4) Stratum lucidum

5) Stratum comeum

What layer is the “extra” layer that is found on the lips, palms, and soles of the feet?

4) Stratum lucidum

Stratum Basale

Consists of a single layer of cuboidal cells in contact with the basement membrane that undergo mitosis; contains pigment-producing melanocytes

Stratum Spinosum

Composed of several layers of cells with centrally located, large, oval nuclei and spinelike processes; limited mitosis

Stratum Granulosum

Composed of one or more layers of granular cells that contain fibers or keratin and shriveled nuclei

Stratum Lucidum

A thin, clear layer found only in the epidermis of the lips, palms, and soles

Stratum Comeum

Consists of many layers of keratinized dead cells that are flattened and nonnucleated; comified

Dermis

Dense, irregular connective tissue containing nerves, blood vessels, and glands of the integument

Hypodermis

Loose connective tissue, largely adipose. Permits movement of the skin and aids in thermoregulation

Functions of the skin

Protection, temp regulation, vitamin d3 synthesis, elimination of waste, reception of stimuli (pain, pressure, temp)

Melanocytes

Melanocytes are specialized cells recognized primarily for their ability to produce melanin, the pigment responsible for color in the skin, hair, and eyes

Where are Melanocytes located?

In the basal layer of the epidermis

What affects the difference in human pigmentation?

The number of melanosomes in keratinocytes and different melanin granule phenotypes

What is the cutaneous nerves for touch?

Meissner corpuscle in papillary layer, it’s a nerve plexus around the hair follicle

What is the cutaneous nerves for pressue?

Pacinian corpuscle in reticular layer

What is the cutaneous nerves for temperature and pain?

Free nerve endings

Arrector Pili

Only muscle of the body wall that receives motor impulses via autonomic nervous system