BIOL 124 Exam 2 George Mason University

Tissue

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

Two basic components of all tissue

1.) Discrete population of cells that are related in structure and function

2.) Extracellular matrix (ECM)

Epithelial Tissue

Sheets of cells that are tightly packed together

Little visible Extracellular Matrix

Cover and line all body surfaces and cavities

Glands

Groups of cells that manufacture and secrete, or release a product such as sweat and saliva

Connective Tissue

Bind, support, protect, and allow the transport of substances through the body

Extracellular Matrix most prominent

Cells are scattered throughout it

Muscle Tissue

Composed of cells that can contract and generate force

Little extracellular matrix

Nervous Tissue

Unique extracellular matrix

Cells can generate, send, and receive messages

Extracellular matrix (ECM)

Composed of the substances surrounding the cells in a tissue

Ground substance and protein fibers

What are the two main components of the extracellular matrix

Ground Substance

Contains interstitial or extracellular fluid with water, ions, nutrients, and other solutes

Contains 3 families of macromolecules: Glycosaminoglycans, proteoglycans, glycoproteins

Glycosaminoglycans (ground substance)

Long, straight polysaccharide chains

Examples include: Chondroitin sulfate and Hyaluronic Acid

Proteoglycans (ground substance)

Consist of glycosaminoglycans bound to a protein core

Resembles a bottle brush

Thousands of _________ can bind in turn to a very long GAG such as hyaluronic acid

Can help make ECM firmer

The aggregates of this also act as a barrier to the diffusion of substances through the ECM

Glycoproteins (ground substance)

Different types together called cell-adhesion molecules (CAMs)

Responsible for adhering the cells both to each other and into their places within the ECM

Help maintain normal architecture of the tissue

Protein Fibers

Composed of multiple fibrous protein subunits that entwine to form long, rope-like structure with a great deal of tensile strength

3 types: Collagen, elastic, and reticular

Collagen, Elastic, Reticular

What are the three types of protein fibers?

Collagen fibers

These proteins make up 20-25% of all protein in the body

Composed of multiple subunits of a fibrous protein

Resembles entwined pieces of steel cable

Very resistant to tension and pressure

Visual: Appear white in gross anatomical specimens such as tendons

Collagen fibers

Elastic fibers

May be stretched to one and a half times their resting length without breaking

When stretching force is removed, they return back to their original length

Comprised of a protein known as elastin that is surrounded by glycoproteins

Distensibilty

The ability of being distended or stretched

Elasticity

The ability of a material to bounce back after being disturbed

Reticular fibers

Type of collagen fiber

Differ in structure, functions, and distribution from the major collagen fibers

Thinner and shorter than regular collagen fibers

Form "webs" in certain organs, such as the spleen, that help these organs trap foreign cells

Marfan Syndrome

Syndrome that results from defects in the gene that codes for a glycoprotein called fibrillin-I

Fibrillin-I is a component of the ECM that is required for the normal deposition

Tight junctions, desmosomes, and gap junctions

What are the three types of cell junctions?

Tight Junctions (Occluding junctions)

Hold cells together, making the spaces between them impermeable and so preventing macromolecules from passing between adjacent cells.

Composed of integral proteins in the plasma membrane of adjacent cells

Desmosomes

Act like button snaps

Materials in the extracellular fluid may pass between cells held together by ___________

Increase the strength of tissue by holding the cells together so that mechanical stress is more evenly distributed

Composed of integral proteins

Found a lot in epithelia because epithelia is subject to a lot of stress

Gap Junctions

Small pores in adjacent plasma membranes formed by protein channels, and they allow small substances to pass freely between the cytosol of two cells

Prominent in cells that can communicate with electrical signals, such as the cardiac muscle

Tight Junction Picture

Desmosomes Picture

Gap Junction Picture

Endocrine

Glands, such as the thyroid, that secrete their products directly into the blood rather than through ducts are classified as....

Osteoblasts

Responsible for bone deposition

Osteoclasts

Responsible for bone resorption

Hyaline Cartilage

If a tissue is composed of many fine collagen fibers that are not visible with a light microscope, has no other type of fiber, and has chondrocytes within lacunae, then the tissue is......

Holocrine Secretion

Glands that accumulate secretions and release them when the cell membranes ruptures, causing cell death, exhibit.....

Lining of the small intestine

Simple columnar epithelium is located in which of the following locations?

Intestines

Stratified Squamous epithelium would not be found in the....

Transitional Epithelia

___________ is a type of tissue consisting of multiple layers of epithelial cells that can contract and expand

Perichondrium

The ____________ is a fibrous connective tissue membrane that covers the external surface of cartilage providing oxygen and nutrients to the chondrocytes

Between Adjacent Vertebrae

Fibrocartilage is found

Ribs and the sternum

Hyaline cartilage is found

In the ear and in parts of the larynx

Elastic Cartilage is found

Blood

The only connective tissue that has a fluid matrix is.....

Air sacs of the lungs

Simple squamous epithelium is found lining the...

Elastic Cartilage

_____________ is found in the external ear

Connective Tissue

Which body tissue consists largely of material outside the cell?

Hyaline Cartilage

If a tissue is composed of many fine collagen fibers that are not visible with a light microscope, has no other type of fiber, and has chondrocytes within lacunae, then the tissue is:

Calcium phosphate crystals

The inorganic portion of bone matrix is composed of

Densely packed protein fibers

Which of the following characteristics is not associated with loose areolar connective tissue?

They are too far away from the blood supply in the dermis

Why do keratinocytes in the superficial strata of the epidermis die?

Stratum Spinosum

What is the thickest layer of the epidermis?

Fibroblasts

Which of the following cells are associated with the dermis?

Basale

The majority of cells in the epidermis arise from mitotic activity in stratum....

Dense irregular connective tissue

What tissue composes the reticular layer of the dermis?

Dendritic Cells

What cells of the epidermis function as phagocytes of the immune system?

Hair follicles

Which of the following structures is not found in thick skin?

Stratum basale of the epidermis

Where are melanocytes located?

Keratinized stratified squamous epithelium

What is the main tissue of the epidermis?

Epidermis and dermis

What are the main components of the cutaneous membrane?

Dense irregular connective tissue

What tissue composes the reticular layer of the dermis?

Stratum basale of the dermis

Where are melanocytes located?

Permanent stretch marks

Extreme stretching of the reticular layer of the dermis results in......

Epithysis

The secondary ossification center in a long bone is located at the....

Infants

Whose bone marrow is mostly red?

Perforating canals

_______ run perpendicular to the osteons

Canaliculi

Which canals connect lacunae together?

Diaphysis

Primary ossification center develop in long bones in the.....

Hyaline cartilage

What tissue serves as the model for bones formed during endochondral ossification?

Trabeculae

Spongy bone is made up of a branching framework called...

Triglyceride storage

The function of yellow bone marrow is ________

Blood vessels and nerve fibers

The canal that runs though the core of each osteon is the site of.....

Femur

All of the following bones are formed by intramembranous ossification except the.....

Osteons

The structural units of mature compact bone are called....

Canaliculi

___________ allow for the passage of oxygen, nutrients, and small substances to and from osteocytes trapped within lacunae

Osteocytes

Bone cells that are surrounded by bone matrix and located with lacunae are.....

Diaphysis

Primary ossification center develop in long bones in the...

Epiphyseal plate

Damage to the _________ in a long bone of a young person might cause the bone to not lengthen properly

Articular cartilage

Which of the following structures persists for life?

Osteoblasts

_______ produce new bone tissue by secreting matrix

Endochondral ossification

_________ forms bone from within a model of hyaline cartilage

Intramembranous ossification

The skull and clavicle form through ___________

Diploe

_______ is the internal layer of spongy bone in flat bones

Epiphysis

The secondary ossification center in a long bone is located at the ____________