Chapter 5

Simple Cuboidal Cells

Squarish or round cells

In this general category of Epithelia, some cells rest on top of other cells and do not contact the basement membrane

Statified Epithelium

What is the most widespread type of stratified epithelium?

Stratified Squamous

Simple Squamous cells

Thin, Scaly cells

Keratinized (cornified) Stratified Squamous Epithelia

This is found in the EPIDERMIS and is covered in a layer of dead compressed-cells. These cells are packed with the durable protein Keratin and coated with a water-repellent glycolipid. It keeps the skin surface relatively dry; retards water loss from the body and resists penetration by disease organisms

Simple Epithelium

This type of epithelium has only one layer of cells. Three types of simple epithelia are named for the SHAPE of their cells: Simple Squamous, Simple Cuboidal, an Simple Columnar

A group of similar cells and cell products that arise from the same region of the embryo and work together to perform specific structural or physiological roles in an organ

Tissue

This type of epithelium was named when it was thought to represent a transitional stage between stratified squamous and stratified columnar epithelium. We now know this is untrue but the name remains.

Transitional Epithelium

What is the fourth type of stratified epithelia?

Transitional Epithelium

True or False: Adipocytes also from in clusters around areolar tissue. The space between adipocytes is occupied by areolar tissue, reticular tissue and blood capillaries

True

There are three PIMARY GERM LAYERS. What are they?

Ectoderm, mesoderm and endoderm

Adipocytes

(Fat cells) Appear in small clusters in some fibrous connective tissues. When they dominate an area, the tissue is adipose tissue.

Hyaluronic Acid

A giant molecule up to 20 micrometers long. It is a viscous, slippery substance that forms a lubricant in joints and constitutes much of the jelly-like VITREOUS BODY of the eyeball

Human develop begins with

A single cell called a fertilized egg, that divides into smaller, identical cells.

The surface that faces away from the basement membrane towards the INTERNAL CAVITY (lumen) of an organ is the

APICAL SURFACE

Epithelia are..............:

AVASCULAR

Chondroitin Sulfate

Abundant in blood vessels and bones and gives cartilage it's relative stiffness. Other GAGs include heparin (anticoagulant) and Hyaluronic Acid

What are the FILTRATION functions of Epithelial tissue?

All substances leaving the blood are selectively filtered through the epithelium that lines the blood vessels; all urinary waste is filtered through the epithelia of the kidneys

Dense IRREGULAR connective tissue

Also has thick bundles of collagen and relatively little room for cells and ground substance, but collagen bundles run in RANDOM DIRECTIONS. This random arrangement allows tissues to resist unpredictable stresses

Adipose tissue

Also known as fat tissue, this is a tissue type in which ADIPOCYTES are the DOMINANT CELL TYPES

Ground substance of fibrous connective tissue

Amid the cells and fibers in some tissue sections, there appears to be a lot of empty space. In life, this space is occupied by a featureless ground substance.

What is a proteoglycan?

Another giant molecule. It is shaped somewhat like a bottle brush, with a central core of protein and bristle-like outgrowths made of GAGs. The entire proteoglycan may be attached to Hyaluronic Acid, which forms a massive molecular complex. Proteoglycans form thick colloids similar to gravy, gelatin and glue. This gel slows the spread of pathogenic organisms through tissues. Some proteoglycans are embedded in the plasma membranes of cells, attached to the cytoskeleton on the inside and other extracellular molecules in the matrix. They create a strong structural bond between cells and extracellular macromolecules that hold tissues together.

There are two types of loose fibrous connective tissue. What are they?

Areolar and Reticular

Some membranes and cobwebby tissues like................are sometimes mounted as.................

Areolar tissue; Spreads

The surface of an epithelial cell that FACES the basement membrane is it's

BASAL SURFACE

Between an epithelium and the underlying connective tissue is a layer called the

BASEMENT MEMBRANE

This contains collagen, glycoproteins, and other protein-carbohydrate complexes and blends into other proteins of connective tissue

Basement Membrane

This serves as an ANCHOR for the epithelium to the connective tissue. It controls the exchange of materials between the epithelium and underlying tissues. It also binds growth factors from below that regulate epithelial development

Basement Membrane

What are the general functions of Connective Tissue?

Binding of organs support physical protection immune protection movement storage heat production

Transport:

Blood transports gases, nutrients, wastes, hormones and blood cells

Areolar tissue is found in tissue sections from almost every part of the body, surrounds.............. and nerves and penetrates with them into small spaces of muscle, tendon and other tissue. Nearly every epithelium rests on a layer of areolar tissue, whose blood vessels provide the epithelium with nutrition, waste removal and ready supply of leukocytes. Leukocytes move freely about areolar tissue

Blood vessels

Movement

Bones provide the lever system for body movement, cartilages are involved in vocal cord movement and cartilages on bone surfaces ease joint movement

Support

Bones support the body; cartilage supports the ears, nose larynx and trachea; fibrous tissues form the framework for organs such as the spleen

Cartilage is produced by cells called

CHONDROBLASTS

In........or............, ground substance can be rubbery or stony in consistency. Generally contains water, gases, minerals, nutrients, wastes, hormones and other chemicals

Cartilage or Bone

Tissues are composed of

Cells and Matrix

What are the components of Fibrous Connective Tissue?

Cells, Fibers and Ground Substance

Plasma Cells

Certain lymphocytes turn into plasma cells when they detect foreign agents. Plasma cells then synthesize disease-fighting proteins called ANTIBODIES. Rarely seen except in the wall of intestines and inflamed tissues.

What is a fixative

Chemicals such as formalin that prevent decay. Post-fixation, most tissues are cut into sections typically only one or two cells thick

What is the most common Glcosaminoglycan?

Chondroitin Sulfate.

There are three types of FIBERS in fibrous connective tissue. What are they?

Collagenous, Reticular and Elastic

Epithelia usually lie on a vessel-rich layer of................., which furnishes them with nutrients and waste removal.

Connective Tissue

Cells of this tissue type occupy LESS space than an extracellular matrix. The cells are usually not in direct contact with each other, but are separated by expanses of the matrix.

Connective Tissues

The most abundant, widely distributed and histologically variable of the primary tissues.

Connective Tissues

Immune protection

Connective tissue cells attack foreign invaders and connective tissue fiber forms a "battlefield" under the skin and mucous membranes where immune cells can be quickly mobilized against disease agents

Most of this tissue type serves to bind organs to each other, form a structural framework for an organ or support and protect organs.

Connective tissues

One cut perpendicular to this is a................(C.S. or X.S) or a transverse section (T.S)

Cross-section

Stratified squamous epithelium

Deepest layer of cells are cuboidal to columnar and include mitotically active stem cells. Their daughter cells push toward the surface and become flatter (more scaly) as they migrate farther upward, until they die and flake off.

Two types of Dense Fibrous Connective Tissues. What are they?

Dense Regular and Dense irregular connective tissue

This type of primary germ layer is an outer layer that gives rise to the epidermis and nervous system

Ectoderm

This primary germ layer is the innermost layer that gives rise to mucous membranes of the digestive and respiratory tracts and digestive glands

Endoderm

What are the ABSORPTION functions of epithelial tissue?

Epithelia absorb chemicals from the adjacent medium; nutrients, for example, are absorbed through the epithelium of the small intestine.

What are the SENSATION functions of epithelial tissue?

Epithelia are provided with nerve endings that sense stimulation ranging from a touch on the skin to the irritation of the stomach.

A high rate of mitosis in Epithelial cells closely positioned to connective tissue allows for:

Epithelia can repair themselves QUICKLY: an ability of special importance in protective epithelia vulnerable to injury such as skin abrasions and erosion by stomach acid

What are the SECRETION functions of epithelial tissue?

Epithelia produce MUCUS, SWEAT, ENZYMES, HORMONES, and most of the body's other secretions. Glands are composed largely of epithelial tissue

What are the PROTECTION functions of epithelial tissue

Epithelia protect deeper tissues from invasion and injury. The epidermis of the skin, for example, is a barrier to infection and the inner lining of the stomach protects it's deeper tissues from stomach acid and enzymes.

What are the EXCRETION functions of epithelial tissue?

Epithelia void wastes from the tissues, such as CO2 across the pulmonary epithelium and bile from epithelium of the liver

This type of tissue consists of a sheet of closely adhering cells, one or more cells thick, with the upper surface usually exposed to the environment or to an internal space in the body

Epithelial Tissue

There are four primary tissue types. What are they?

Epithelial, Connective, nervous and muscular

This layer covers the body surface, lines body cavities, forms the external and internal linings of many organs and constitutes most gland tissues

Epithelium

Study of exfoliated cells is

Exfoliate Cytology

Loss of Stratified Squamous is called

Exfoliation (Desquamation)

Areolar loose connective tissue

Exhibits loosely organized fibers, abundant blood vessels and a lot of seemingly empty space. Possesses all six cell types previously discussed. It's fibers run in random directions and are mostly collagenous, but elastic and reticular are also present. Highly variable in appearance. Often difficult to distinguish from dense irregular connective tissue

This is the body's primary energy reservoir

Fat

Storage

Fat is the body's major energy reserve; bone is a reservoir of calcium and phosphorus that can be drawn upon as needed

Dense fiber connective tissue

Fiber occupies more space than cells and ground substance; appears closely packed in tissue sections

Matrix is composed of

Fibers and ground substance

What are the Fibrous connective tissue cell types?

Fibroblasts Macrophages Leukocytes Plasma Cells Mast Cells Adipocytes

The matrix of a cell is composed of

Fibrous proteins and usually a clear gel known as GROUND SUBSTANCE, tissue fluid, extracellular fluid or even interstitial fluid

This is the most diverse type of connective tissue, also called fibroconnective tissue

Fibrous tissue

Connective tissues include:

Fibrous tissue, adipose tissue, cartilage, bone and blood.

Mature connective tissues

Fibrous, adipose, supportive and fluid

There are four categories of mature connective tissue. What are they?

Fibrous, adipose, supportive and fluid connective tissue

Tissue specimens are preserved in a

Fixative

Mesenchyme

Form of embryonic connective tissue

Elastic tissue

Forms wavy sheets in large and medium ARTERIES. When the heart pumps blood into the arteries, sheets enable them to expand and relieve some pressure on smaller arteries downstream. When the heart relaxes, arterial wall springs back and keeps blood pressure from dropping too low between heartbeats.

Brown fat

Found mainly in FETUSES, INFANTS AND CHILDREN. Accounts for up to 6 percent of an infant's weight. Concentrated in fat pads in the shoulders, upper back and around the kidneys. Brown fat stores lipid in the form of multiple globules rather than one large one. Gets color from unusual abundance of blood vessels and enzymes in the mitochondria

Brown fat is:

HEAT GENERATING TISSUE! Numerous mitochondria, but oxidative pathway is NOT LINKED TO ATP SYNNTHESIS. When cells oxidize, energy is RELESED AS HEAT!

Most tissue samples under a microscope on a slide are thin slices called

Histological sections

These are artificially colored to bring out fine detail

Histological sections

The study of tissues and how they are organized into organs

Histology

Many anatomical structures are longer on one axis than another, the............and...............are good examples of this. A tissue cut on it's long axis is called a LONGITUDINAL SECTION (L.S)

Humerus and esophagus

Transitional Epithelium

Interesting type of stratified epithelium because it is really limited to the urinary tract.

Why is sectioning specimens necessary?

It is essential to allow light of a light microscope to pass through so the image is not confuse by too many layers of overlapping cells. Sections are then mounted on slides and artificially colored with histological stains used to enhance detail

There are two kinds of stratified squamous epithelia. What are they?

Keratinized and non-keratinized

First tissues begin when cells organize themselves into.........., first two and then three strata called PRIMARY GERM LAYERS

LAYERS

Once enclosed in the..............., the cells are called CHONDROCYTES.

Lacunae

Fibroblasts and their function in Fibrous connective tissue:

Large, fusiform or stellate cells that often show slender, wispy branches. They produce the fibers and ground substance that form the matrix of the tissue

Macrophages

Large, phagocytic cells that wander through connective tissues, where they engulf and destroy bacteria, other foreign particles and dead or dying cells of our own body. They also activate the immune system when they sense foreign matter called antigens. They arise from WHITE BLOOD CELLS called MONOCYTES or from the same stem cells that produce monocytes

What are glycosaminoglycans?

Long polysaccharides composed of unusual dissacharides called amino sugars and uronic acid. GAGs are negatively charged and tend to attract SODIUM and POTASSIUM ions, which in turn cause GAGs to absorb and retain water. They play an important role in regulating water and electrolyte balance of tissues

There are two broad categories of fibrous connective tissue. What are they? What differentiates the two?

Loose and Dense fibrous connective tissues. Determined based on relative abundance of fiber

Epithelial cells closest to the connective tissue typically exhibit a high rate of:

MITOSIS

What are the pathologies associated with deficiencies in Elastic tissue?

Marfan syndrome and artherosclerosis

This gives to muscle, bone, blood and other tissues. Most organs are composed of tissues derived from two or more primary germ layers

Mesenchyme

This is a gelatinous tissue made of FINE, WISPY COLLAGEN (PROTEIN) FIBERS and branching mesenchymal cells embedded in gel-like ground substance

Mesenchyme

Reticular tissue

Mesh of reticular fibers and fibroblasts. Forms the framework (Stroma) of organs such as lymph nodes, spleen, thymus and bone marrow. Space amid fibers is filled with BLOOD CELLS

This type of primary germ layer is a layer of loosely organized cells and eventually turns into a gelatinous tissue called MESENCHYME

Mesoderm

Heat production

Metabolism of brown fat generates heat in infants and children

Histology can also be called

Microscopic Anatomy

White fat (Or yellow)

More abundant than brown fat and is the only significant adipose tissue in the adult human body. Large, single central globule of triglyceride. The cytoplasm is otherwise restricted to a thin layer immediately beneath the plasma membrane, with the nucleus pushed against the edge of a cell. The triglyceride is dissolved out by most histological fixations; fat cells in most specimens look empty and somewhat collapsed

If left unstained:

Most tissue sections would appear pale gray

Loose fibrous connective tissues

Mostly space occupied by ground substance, which dissolves out of tissue during histological fixation and leaves empty space in prepared tissue sections.

Dense Regular Connective Tissue

Named for two properties: Collagen fibers are closely packed and leave relatively little open space. Fibers are PARALLEL to each other. This tissue is found especially in tendons and ligaments

Pseudostratified Columnar Simple Epithelia?

Not all Cells reach the surface and shorter cells are covered by taller ones. This epithelium looks stratified in most tissue sections, but under examination with TEM, shows that EVERY CELL reaches the basement membrane.

A section cut on a SLANT between a longitudinal and cross section is an

OBLIQUE SECTION

A............is an exam of exfoliated cells from the cervix for signs of uterine cancer

Pap Smear

These layers give rise to all of the body's MATURE TISSUES

Primary germ layers

Goblet Cells

Produce protective mucous coatings over mucous membranes. They have expanded apical ends filled with SECRETORY VESICLES; their product becomes mucus when it is secreted and absorbs water. The basal part of the goblet cell is a narrow stem that reaches the basement membrane

What are the functions of epithelial tissue?

Protection Secretion Excretion Absorption Filtration Sensation

Adhesive Glycoproteins

Protein-carbohydrate complexes that bind plasma membrane proteins to extracellular collagen and proteoglycans. They bind components of a tissue together and make paths that guide migrating embryonic cells to destinations in a tissue.

What is the fourth type of simple epithelia?

Pseudostratified Columnar

Stratified Epithelia

Range from 2-20 or more layers of cells, with some cells resting directly on others and only the deepest layer attached to the basement membrane

Stratified Columnar Epithelia

Rare and relatively minor in importance. Seen only in places where two other epithelial types meet. It is limited to regions of the pharynx, larynx, anal canal and male urethra

This tissue is laid out on the slide, like placing a small square of tissue paper

Spreads

Cartilage

Relatively stiff connective tissue with flexible rubbery matrix. The Adam's Apple is thyroid cartilage of the larynx

Epithelia are classified into two broad categories:

SIMPLE AND STRATIFIED

Chondroblasts

Secrete the matrix and surround themselves with it until trapped in small cavities called LACUNAE

Doing this to a tissue reduces a 3-D structure to a series of 2-D structures.

Sectioning

What is the function of Cartilage?

Shape and support the ears and nose and particularly enclose the larynx (VOICE BOX), trachea (WINDPIPE) and thoracic cavity

.............and............epithelia often have wineglass-shaped GOBLET CELLS

Simple Columnar; Pseudostratified Columnar

In this general category of Epithelia, every cell touches the basement membrane.

Simple Epithelium

What does sectioning mean?

Slicing

Three fourths of the stratified epithelia are named for shapes of the surface cells. What are they?

Stratified squamous, stratified cuboidal, stratified columnar.

Deeper cells of stratified epithelia may be a different shape than the..................

Surface Cells

Simple Columnar Cells

Tall, narrow cells

Binding of Organs

Tendons bind muscle to bone, ligaments bind one bone to another, fat holds kidneys and eyes in place and fibrous tissue binds skin to underlying muscle

Dense irregular connective tissue constitutes

The DERMIS, where it binds skin to underlying muscle and connective tissue. Forms protective capsule around organs such as kidneys, testes and spleen, tough fibrous sheath around bones, nerves and most cartilage

The best anatomical insight depends on:

The ability to deduce the 3-d structure of an organ from 2-d sections

Physical protection

The cranium, ribs and sternum protect delicate organs such as the brain, lungs and heart; fatty cushions protect kidneys and the eyes

Nonkeratinized

The tongue, esophagus, vagina and other internal membranes are covered by this. It lacks surface layer of dead cells. Provides a surface that is abrasion-resistant, but moist and slippery. Well-suited to resist stress by chewing and swallowing and sexual intercourse/childbirth

Avascular:

There is no room between the cells for blood vessels

Collagenous

These are fibers made from collagen that are tough, flexible and resist stretching. Collagen is the body's most abundant protein. In fresh tissue, collagenous fibers have a glistening white appearance, as seen in some tendons and some cells of meat. They are often called white fibers. In tissue sections, collagen forms COARSE, WAVY BUNDLES, often dyed pink, blue or green by stains. Tendons, ligaments and the DERMIS of the skin are made primarily from collagen. Less visibly, collagen pervades the matrix of cartilage and bone

Reticular Fibers

These are thin collagen fibers coated with glycoprotein. They form a sponge-like framework for organs such as the spleen and lymph nodes.

Elastic fibers

These are thinner than collagenous fibers and they branch and rejoin each other along their course. They are made of a protein called ELASTIN, whose coiled structure allows it to stretch and recoil like a rubber band. Elastic fibers account for the ability of skin, lungs and arteries to spring back after they are stretched.

Mast cells

These cells, found alongside blood vessels, secrete a chemical called HEPARIN, which inhibits blood clotting and one called HISTAMINE, which increases blood flow by dilating blood vessels

What differentiates the four tissue types from each other?

They all differ in types and functions of their cells, the characteristics of the matrix (extracellular material) that surrounds he cells and relative amount of space occupied by the cells and matrix. Example: In muscle and epithelium, cells are so close together that the matrix is scarcely visible, but in connective tissues, the matrix usually occupies more space than cells do.

True or False: Cartilage rarely exhibits blood vessels and even when it does, the blood vessels are just passing through without giving off capillaries to nourish the tissue. Therefore, nutrition and waste removal depend on solute diffusion through the stiff matrix. Because this is a slow process, chondrocytes have slow rates of metabolism and cell division, meaning cartilage heals slowly.

True

True or False: Cells and extracellular material of epithelium can be loosely compared to bricks and mortar of a wall. The EXTRACELLULAR MATERIAL ("mortar") is so thin, that it can barely be visible under a light microscope and cells appear close together.

True

True or False: Connective tissues vary greatly in vascularity, from rich networks of blood vessels in loose connective tissues to few or no blood vessels in cartilage.

True

True or False: Nearly all connective tissues contain fibers, but the fibers considered in tissues here are classified together because they are so conspicuous. Fibers are just one component of tissues, which also consist of cells and ground substance

True

True or False: Not all histological preparations are sections. Liquid tissues such as blood, soft tissues such as spinal cord may be prepared as SMEARS, in which the tissue is rubbed or spread across a slide rather than sliced

True

True or False: Stored fat is not necessarily stagnant. New triglycerides are always synthesized and stored as others are hydrolyzed and released into circulation. This means there is constant turnover of stored triglycerides with an equilibrium between synthesis and hydrolysis

True

True or False: The parallel arrangement of fibers is an adaption to the fact that tendons and ligaments are pulled in predictable directions by musculoskeletal stresses. With minor exceptions such as blood vessels and sensory nerve fibers, only cells in DENSE CONNECTIVE TISSUES ARE FIBROBLASTS, which are easily distinguished by slender, violet staining nuclei squeezed between bundles of collagen. Few blood vessels in Dense connective tissues, so tendons and ligaments are slow to heal

True

True or False: Within the two broad categories of Epithelia, being simple and stratified, there are four subcategories.

True

Why would the transitional epithelium be limited to the urinary tract?

Urine is usually acidic and hypertonic to intracellular fluid. It would tend to draw water out of cells via osmosis and kill them if there were nothing to protect the cells. Domed surface of cells in transitional epithelium have a unique protective property called UMBRELLA CELLS. On the upper surface of an umbrella cell, the outer phospholipid bilayer of the plasma membrane is thicker than usual and has dense patches called lipid rafts with embedded proteins called UROPLAKINS. Uroplakins are impermeable to urine and protect the epithelium, including the cytoplasm of the umbrella itself. Lipid rafts are connected to each other by hinges of ordinary plasma membrane. When the bladder is empty and relaxed, these plaques fold at the hinges and drop into the cell interior for storage, causing the cell to bulge upward. As the bladder fills, hinges open, plaques spread out over the surface to protect the cell and umbrella cell becomes thinner and flatter.

Ground substance

Usually has gelatinous or rubbery consistency resulting from 3 classes of large molecules: glycosaminoglycans, proteoglycans and adhesive glycoproteins. These absorb COMPRESSIVE FORCES and protect delicate cells from mechanical injury

The.............and some spinal ligaments are made of DENSE REGULAR connective tissue called ELASTIC TISSUE. In addition to densely packed collagen fibers, elastic tissue exhibits branching elastic fibers and more fibroblasts. These specific fibroblasts have larger, more conspicuous nuclei than most dense regular connective tissue

Vocal Cords

This fat type provides thermal insulation, anchors and cushions organs such as the eyeballs and kidneys and contributes to body contours such as hips and breasts

White Fat

Leukocytes, or White Blood Cells

White blood cells travel briefly in the bloodstream, then crawl out through the walls of small blood vessels and spend most time in connective tissues. Two of the most common types are NEUTROPHILS, which wander about attacking bacteria and LYMPHOCYTES, which react against bacteria, toxins and other foreign agents. Lymphocytes often form dense patches in mucous membranes.

There are two kinds of fat in humans. What are they?

White fat (or yellow) and Brown Fat