A&P Test 2

Tissue

Group of structurally and functionally related cells and their external environment that together perform common functions

All tissues share:

1. A discrete population of cells that are related in structure and functions

2. ECM

Epithelial tissue

• sheets of tightly packed cells

• little visible ECM

• cover and line body structures and cavities

• specialized epithelial cells form glands

Connective tissue

• connects all other tissues in the body to one another

• ECM is the most prominent feature

• bind, support, protect and allow transport of substances

Muscle tissue

• cells that contract and generate force

• little ECM

Nervous tissue

• unique ECM

• cells generate, send, and receive signals

ECM

Substance in a tissue outside the cells that consist of extracellular fluid, ground substance, and protein fibers

The two components of the ECM are:

• ground substance

• protein fibers

Functions of ECM:

• provide tissue with strength to resist tensile stretching and compressive forces

• directing cells to their proper places within a tissue

• regulating the development, mitotic activity, and survival of cells

• holding cells in their proper position

3 types of protein fibers in the ECM:

• collagen

• reticular fibers

• elastic fibers

High tensile strength

Ability to resist tension and pressure from pulling and stretching forces

Collagen has a high:

Tensile strength

Distensibility

Stretching longer than resting length

Elasticity

Returning to original length when the stretching force is removed

Elastic fibers exhibit:

Distensibility and elasticity

Fibers that interweave to form a netlike supporting structure

Reticular fibers

Epithelial tissues are found:

In every internal and external body surface

Functions of epithelial tissues

• Protection (uses keratin to shield tissues from mechanical and thermal injury)

• Immune defenses (specialized cells create barriers against microorganisms)

• Transport into other tissues (selectively permeable)

• Sensation (nerves detect change in environments)

In a microscope nuclei are identified by:

Dark purple circles

In a microscope ground substance is identified by:

Clear/ slightly tinted substance

In a microscope proteins are identified by:

Straight/wavy lines (ex. collagen = pink wavy lines that lack a nuclei)

In a microscope red blood cells are identified by:

Clustered, small, light red, round discs that lack a nuclei

Avascular

Lacking blood vessels (ex. epithelial cells)

Oxygen and nutrients get to epithelial tissue by:

Diffusion of the nutrients from blood in tissue below it (connective tissue)

The thickness of epithelial tissues is impacted by:

It’s avascular nature (if the blood vessels are too far away then the nutrients won’t be able to reach it through diffusion)

How much ECM is in epithelial tissues?

Essentially none

ECM in epithelial tissues is located in the:

Basement membrane

Basement membrane functions:

• “glue” the epithelial tissue to the underlying connective tissue

• anchors underlying blood vessels in place

• provides a barrier between epithelial tissue and underlying tissue

Apical surface

Top/ free edge of epithelial tissue

Basal surface

Edge attached to deeper cells

Epithelial tissues are classified in two ways:

1. Shape of cells

2. Number of layers

Number of epithelial layers can be classified as:

• simple (1 layer)

• stratified (more than 1)

Shape of epithelial cells can be classified as:

• squamous

• cuboidal

• columnar

Function of simple epthelia

• not very resistant to mechanical stress because they are thin (not good outer barriers)

• thin structure allows substances to diffuse and be transported

Simple squamous functions

• rapid diffusion of oxygen and carbon dioxide

• produces serous fluid

Simple squamous location

• air sacs of lungs

• lines body cavities

Simple cuboidal functions

• absorption

• secretion

Simple cuboidal location

• kidney tubules

• glands

Simple columnar functions

• with microvilli: absorption

• with cilia: propulsion of egg

Simple columnar location

• small intestine

• uterine tube

Pseudostratified columnar functions

Ciliated: secretes and propels mucus

Pseudostratified columnar location

• nasal cavity

• trachea

Paracellular transport

Substances pass through the narrow space between cells in simple epithelia

Transcellular transport

1. Substance centers the cells via active or passive means

2. Substance diffuses through the cytosol

3. Substance exits the other surface of the cell via active or passive means

*transport in simple epithelia

Stratified epithelia functions

• effective protective barriers due to thickness (multiple layers)

• found in areas with a high degree of mechanical stress

Stratified epithelia are named by the shape of their cells in the:

Apical layer

Stratified squamous functions

• keratinized: protection from abrasion and prevents water loss through the skin

• nonkeratinized: protection from abrasion

Stratified squamous locations

• keratinized: epidermis

• nonkeratinized: mouth and vagina

Stratified cuboidal functions

Secretion

Stratified cuboidal locations

Sweat glands

Transitional functions

Stretches

Transitional locations

Urinary bladder

Gland

Structure that makes and secretes a product

Glands arise from:

Epithelial tissue that grows inward into the underlying CT

Secretory cells

Cells of the gland that manufacture and release the product

Exocrine gland

Secrets product through a duct to the external surface

Endocrine gland

Secretes hormones directly into the bloodstream to influence the functions of distant target cells

Unicellular exocrine gland

• composed of a single cell

• simplest gland

• ex. goblet cell (secretes mucus)

Multicellular exocrine gland

• most common type of exocrine gland

• made of clusters of secretory cells arranged in different ways

Merocrine secretion

• exocrine secretion

• product is released by exocytosis

Holocrine secretion

• exocrine secretion

• shed and ruptured epithelial cells release products

• product accumulates in secretory epithelial cells

• epithelial cells undergo mitosis to replace shed cells

Pectoral girdle function

Support the upper limb

The bones that compose the pectoral girdle are the:

Clavicle (collarbone) and scapula

Sternal end of the clavicle

• medial end

• articulates with the manubrium of the sternum forming the sternoclavicular joint

Acromial end of the clavicle

• lateral end

• articulates with the acromion of the scapula to form the acromioclavicular joint

What shape does the clavicle look like from a superior/inferior view?

S-shaped

Fractures of the clavicle occur from:

• direct trauma or falling onto an outstretched arm

• the arm falls anteriorly and medially

Shape of scapula

Triangular

The spine of the scapula is a continuation of the:

Acromion

What side is the spine of the scapula located?

posterior side

Depression above the spine

Supraspinous fossa

Depression below the spine of the scapula

Infraspinous fossa

Glenoid cavity

Lateral depression (small indentation) of the scapula that articulates with the humerus at the shoulder joint

Coracoid process

• resembles a bent little finger

• projection on the anterior side of the scapula

Subscapular fossa

• inferior to the coracoid process

• depression on the anterior side of the scapula

Connective tissue functions

• connecting and binding (connect structures in the body and bind tissue layers and anchor organs in place)

• support (bone and cartilage support the weight of the body)

• protection (bone tissue protects organs and cartilage and fat provides shock absorption, also elements of immune system are found)

• transport (blood is the main transport in the body)

All connective tissue has what in common?

ECM

CT proper

• functions to connect and support other tissues

• widely distributed in the body

• forms part of the internal structure of some organs

Cells in CT proper

• fibroblasts

• adipocytes

• mast cells

• phagocytes

• other immune cells

Fibroblasts

• produce protein fibers and ground substance (components of ECM)

Adipocytes

• fat cells that store lipids

• cells contain large lipid droplet in the cytoplasm

Mast cells

• immune system cells involved in inflammation

• tissue-bound immune cell

• largest resident cells

Phagocytes

• immune system cells that ingest foreign substances

• phagocytosis

• ex. macrophages (ingest damaged cells, bacteria, and cellular debris)

Other immune cells

Cells of the immune system migrate in and out of different CT depending on the needs of the body

Another term for loose CT is:

Areolar CT

Primary component of loose CT

Ground substance

Location of loose CT

• deep to the epithelium of the skin

• membranes lining the body cavities

• layers in the walls of hollow organs

Loose CT functions

• support

• contains blood vessels to diffuse nutrients and oxygen up to the superficial epithelial cells

• houses numerous immune cells that protect against microorganisms invading the epithelium

Primary component of dense CT

Protein fibers

Types of dense CT

• irregular CT

• regular collagenous CT

• regular elastic CT

Primary component in dense irregular CT

Collagen fiber

Arrangement of dense irregular CT

• Haphazard arrangement makes it strong and allows it to resist tension in all 3 planes

Location of dense irregular CT

• dermis

• around organs and joints

• in areas subject to tension

Primary component of dense regular collagenous CT

Collagen

Arrangement of dense regular collagenous CT

• parallel arrangement of collagen fibers

• oriented in a single direction which makes them strong and able to resist tension in one direction

Location of dense regular collagenous CT

• tendons (join muscle to bone)

• ligaments (join bones)

Primary component in elastic tissue

Parallel elastic fibers mainly (also has randomly oriented collagen fibers)

Location of elastic tissue

• lining of large blood vessels

• certain ligaments (ex. spine)

Structure of reticular tissue

• reticular fibers produced by surrounding fibroblasts

• thin reticular fibers interweave to form weblike nets to support small structures like blood and lymphatic vessels

Location of reticular tissue

• lymph nodes

• spleen

• forms part of the basement membrane in epithelia

• internal structure of the liver and bone marrow