Tissues
Are groups of cells that are similar in structure and perform a common or related function
-Four primary tissue types interweave to form the "fabric" of the body: epithelial, connective, nervous, and muscle tissue
Primary tissue in a single word
-Epithelial tissue: Covers
-Connective tissue: Supports
-Nervous Tissue: Controls
-Muscle Tissue: Produces movement
Histology
The study of tissues complements the study of gross anatomy
Before a specimen can be viewed through a microscope
-Specimen must be fixed (preserved)
-Then cut into sections (slices) thin enough to transmit light or electrons
-Lastly, the specimen must be stained to enhance contrast
Epithelial tissue/ epithelium (epithelia)*
Is a sheet of cells that covers a body surface or lines a body cavity
-Two forms occur in the body: covering and lining epithelium & glandular epithelium
-Accomplishes many functions, including (1) protection, (2) absorption, (3) filtration, (4) excretion
Covering and lining epithelium
Forms the outer layer of the skin; dips into and lines the open cavities of the urogenital, digestive, and respiratory systems; and covers the walls and organs of the closed ventral body cavity
Glandular epithelium
Fashions the glands of the body
Epithelial five distinguishing characteristics
Polarity, specialized contacts, supported by connective tissues, being avascular but innervated, and having the ability to regenerate
Apical surface*
All epithelia have an _______ _______, an upper free surface exposed to the body exterior or cavity of an internal organ, and a lower attached
-Open to the air/outside
Basal surface (simple)*
A epithelia also has a lower attached ________ _________
-Simple: Only one cell layer thick
-Basement membrane; faces the basal membrane. It is connected to connective tissue through diffusion
Basal surface (stratified)*
A epithelia also has a lower attached ________ _________
-Stratified: More than one cell later thick; one cell layer thick and add on
-Connected to the basement membrane and nutrient source
-Slower rate to get oxygen (inside/middle of the basal surface)
-
Brush border
In epithelia that absorb or secrete (export) substances (those lining the intestine or kidney tubules, for instance), the microvilli are often so dense that the cell apices have a fuzzy appearances
Basal lamina*
Adjacent to the basal surface of an epithelium is a thin supporting sheet
-This noncellular, adhesive sheet consists largely of glycoproteins secreted by the epithelial cells plus some fine collagen which molecules diffusing from the underlying connective
Specialized Contacts
Lateral contacts, including tight junctions and desmosomes, bind adjacent cells together at many points
Tight Junctions*
Help keep proteins in the apical region of the plasma membrane from diffusing into the basal region, and thus help to maintain epithelial polarity
-Impermeable junctions to but cells together so molecules won't go in
-Desmosomes: Anchoring junctions bind
Intermediate filaments (keratin)*
Makes intermediate fibers
-Tough, insoluble protein fibers constructed like woven ropes
Reticular lamina
Just deep to basal lamina that is a layer of extracellular material containing a fine network of collagen protein fibers that "belongs to" the underlying connective tissue
Basement membrane
The two laminae form the _________ __________, which reinforces the epithelial sheet, helps it resist stretching and tearing, and defines the epithelial boundary
Avascular
Epithelium that contains no blood vessels
Innervated
Epithelium that is supplied by nerve fibers
Regeneration
Epithelium has a high regenerative capacity
Simple epithelia
Consists of a single cell layer. They are typically found where absorption, secretion, and filtration occur and a thin epithelial barrier is desirable
Stratified epithelia
Composed of two or more cell layers stacked on top of each other, are common in high-abrasion areas whereas where protection is important, such as the skin surface and the lining of the mouth
Squamous cells
Are flattened and scalelike; flattened disc
Cuboidal cells
Boxlike, approximately as tall they are wide; spherical
Columnar cells
Are tall and column shaped; nucleus is elongated from top to bottom and usually located closer to the cell base
Simple epithelia
Most concerned with absorption, secretion, and filtration
-Consist of a single cell layer and usually very thin, therefore protection is not one of their specialities
Simple Squamous Epithelium*
Flattened laterally, and their cytoplasm is sparse
-Surface view: cytoplasm is sparse a tiled floor
-Cell cut perpendicular to their free surface: Resemble fried eggs seen from the side, with their cytoplasm wisping out from the slightly bulging nucleus
-
Two simple squamous epithelia in the body have special names that reflect their location
Endothelium and Mesothelium
Endothelium*
Provides a slick, friction-reducing lining in lymphatic vessels and in all hollow organs of the cardiovascular system-blood vessels and the heart. Capillaries* consist exclusively of endothelium, and its exceptional thinness encourages the efficient excha
Mesothelium*
Is the epithelium found in serous membranes, the membranes lining the ventral body cavity and covering its organs
Simple Cuboidal Epithelium*
Consists of a single layer of cells as tall as they are wide. The Spherical nuclei stain darkly, causing the cell layer to look like a string of beads when viewed microscopically
-Functions: Secretion and absorption. Also forms the walls of the smallest d
Simple Columnar Epithelium*
Single layer of tall, closely packed cells, aligned like soldiers in a row. It lines the digestive tract from the stomach through the rectum.
-Help move substances or cells through an internal passageway (food goes through this protein)*
-Columnar cells:
Psuedostratified Columnar Epithelium*
Vary in height. All of its cells rest on the basement membrane, but only the tallest reach the free surface of epithelium
-The tissues give the false impression that several layers are present ("fake" stratified)*
-The short cells are relatively unspecial
Stratified Sqaumous Epithelium (non-keratinized)*
Widespread of the stratified epithelia
-Composed of several layers, it is thick and well suited for its protective role in the body
-Its free surface cells are squamous, and cells of the deeper layers are cuboidal or columnar
-Wear and tear, and its surfa
Stratified Cuboidal epithelium
Rare in the body, mostly found in the products of some of the larger glands (sweat glands, mammary glands)
-Two layers of cuboidal cells
Stratified Columnar epithelium
Has a limited distribution in the body
-Small amounts found in the pharynx, the male uretha, and lining some glandular ducts.
-Occurs at transition areas or junctions between two other types of epithelia, only its apical layer of cells is columnar
Transitional epithelium*
Forms the lining of hollow urinary organs, which stretch as they fill with urine
-Cells of its basal layer are cuboidal or columnar. Apical cells vary in appearance, depending on the degree of distention (stretching) of the organ
-Function: Stretches read
Gland
Consists of one or more cells that make and secrete a particular product
Secretion
Is an aqueous (water-based) fluid that usually contains proteins, but there is variation
-Active process: Glandular cells obtain needed substances from the blood and transform them chemically into a product that is then discharged from the cell
Glands two sets of traits
-They release their product-glands may be endocrine (internally secreting) or exocrine (externally secreting)
-Relative cell number-glands may be unicellular ("one-celled") or multicellular ("many-celled")
Endocrine glands*
Eventually lose their ducts, they are often called ductless glands. They produce hormones (inside).
-Diabetes: Insulin
Hormones
Messenger chemicals that they secrete by exocytosis directly into the extracellular space
-Enter the blood or lymphatic fluid and travel to specific target organs
Exocrine glands*
Secrete their products onto body surfaces (skin) or into body cavities
-A diverse lot and many of their products are familiar
-Include: Mucous, sweat oil, and salivary glands, the liver (which secretes bile), the pancreas (which synthesizes digestive enzy
Unicellular exocrine glands
Mucous cells and goblet cells. They are sprinkled in the epithelial linings of the intestinal and respiratory tracts amid columnar cells with other functions
Mucin
All glands produce this which is a complex glycoprotein that dissolves in water when secreted. Once dissolved, mucin form mucus, a slimy coating that protects and lubricates surfaces
Goblet cells
The cuplike accumulation of mucin distends the top of the cell, making the cells look like a glass with a stem
Multicellular Exocrine Glands
Structurally complex; Have two basic parts: an epithelium-derived duct and a secretory unit (acinus) consisting of secretory cells. Supportive connective tissue surrounds the secretory unit and supplies it with blood vessels and nerve fibers, and forms a
Structural classification
on the basis of their duct structures, multicellular exocrine glands are either simple or compound. The glands are further categorized by their secretory units as (1) tubular, (2) alveolar, or (3) tubuloalveolar
Simple glands
Has an unbranched duct
Compound glands
Have branched duct
Tubular
If the secretory cells form tubes
Alveolar
If the secretory cells form small, flask like sacs
Tubuloalveolar
If they both (alveolar and tubular) have types of secretory units
Acinar
Used interchangeably with alveolar
Modes of secretion
Multicellular exocrine glands secrete their products in different ways, so they can be also be described functionally as merocrine, holocrine, or aprocrine
Merocrine glands
Secrete their products by exocytosis as they are produced. The secretory cells are not altered in any way. The pancreas, most sweat glands, and salivary glands belong to this class
Holocrine glands
Accumulate their products within them until they rupture. Include the synthesized product plus dead cell fragments, "die for their cause." Example: Sebaceous (oil) glands of the skin
Aprocrine glands
Present in other animals and may or may not be in humans as a third gland type. Accumulate their products only beneath the free surface. Eventually, the apex of the cell pinches off, releasing the secretory granules and a small amount of cytoplasm. The ce
Connective tissues
Most abundant and widely distributed of the primary tissues, but its amount in particular organs varies.
Four main classes of connective tissues
(1) connective tissue proper, (2) cartilage, (3) insulating, and (4) blood
Connective tissue major functions
(1) binding and supporting, (2) protecting, (3) insulating, (4) storing reserve fuel, and (5) transporting substances within the body
Three characteristics of connective tissues
Common origin, degree of vascularity, and extracellular matrix
Common origin
All connective tissues are arise from mesenchyme (an embryonic tissue)
Degree of vascularity
Connective tissues run the the gamut of vascularity. Cartilage is avascular. Dense connective tissue is poor vascularized, and other types of connective tissue have a rich supply of blood vessels
Extracellular matrix*
Nonliving which widely separates the living cells of the tissue. It can bear weight, withstand great tension, and endure abuses, such as physical trauma and abrasion that no other tissue can tolerate
-Ground substance and fibers make this
-Fibers in a bal
Connective tissues three main elements
Ground substance, fibers and cells
Areolar connective tissue
Is the prototype and model with a common structural plan with connective tissues
Ground substance
Unstructured material that fills the space between the cells and contains the fibers. Composed of interstitial (tissue) fluid, cell adhesion proteins, and proteoglycans.
-Consists of large amounts of fluid and functions as a molecular sieve, or medium, th
Cell adhesion proteins
serve mainly as a connective tissue glue that allows connective tissue cells to connect to the matrix elements
Proteoglycans
Consist of a protein core to which glycosaminoglycans (GAGS) are attached. Tend to form huge aggregates in which GAGS interwine and trap water, forming a substance that varies from a fluid to a viscous gel. The higher the GAG content, the more viscous the
Three types of Connective Tissue Fibers
Collagen fibers, elastic fibers and reticular fibers
Collagen fibers*
Constructed primarily of the fibrous proteins collagen. Collagen molecules are secreted into extracellular space, where they assemble spontaneously into cross-linked fibrils, which in turn are bundled together into the thick collagen fibers seen with a mi
Elastic fibers*
Long, thin fibers that form branching net-works in the extracellular matrix. Contain a rubber-like protein, elastin, that allows them to stretch and recoil like rubber bands only before its thick, ropelike collagen fibers become taut. When there is tensio
Reticular fibers*
Short, fine, collagenous fibers with a slightly different chemistry and form. Continuous with collagen fibers, and they branch extensively, forming delicate networks that surround small blood vessels and support the soft tissue of organs
-Loose
Connective Tissue Cells*
Exists in immature and mature forms. Immature cells are actively mitotic cells that secrete the ground substances and the fibers characteristic of their particular matrix
Primary blast cell types by connective tissue class
(1) connective tissue proper: fibroblast; (2) cartilage: chondroblast; (3) bone: osteoblast
Hematopoietic stem cell
The undifferentiated blast cell that produces blood cells because it is not located in "its" tissue (blood) and does not make the fluid matrix (plasma) of that tissue.
White blood cells*
-Neutrophilis* (immune system cell), eosinophilis, lymphocytes
-Other cell types that are concerned with tissue response to injury
Mast cells*
Cluster among blood vessels. The oval cells detect foreign microorganisms (e.g., bacteria, fungi) and initiate local inflammatory responses against them. Inside, cytoplasm are secretory granules containing chemicals that mediate inflammation (especially s
Heparin
An anoticoagulant chemical that prevents blood clotting when free in the bloodstream
Histamine
A substance that makes capillaries leaky
Protease
Protein-degrading enzymes
Macrophages (connective)*
Large, irregular shaped cells that avidly phagocytize a broad variety of foreign materials, ranging from foreign molecules to entire bacteria to dust particles. Dispose dead cells and central actors in the immune system. Peppered throughout loose connecti
Mesenchyme*
Mature connective tissues arise from a connective embryonic tissue. Has a fluid ground substance containing fine sparse fibers and star-shaped mesenchymal cells. Begins in embryonic development and differentiates into all other connective tissue or produc
Connective tissue proper*
Loose connective tissues (areolar, adipose, and reticular) and dense connective tissues (dense regular, dense irregular, and elastic). Except for bone, cartilage, and blood, all mature connective tissues are connective tissue proper
Areolar (loose) Connective Tissue*
-Supporting and binding other tissues (the job of the fibers)
-Holding body fluids (the ground substances's role)
-Defending against infection (via the activity of white blood cells and macrophages)
-Storing and nutrients as fat (in fat cells)
-Distribute
Fibroblasts*
Flat branching cells that appear spindle shaped in profile, predominate, but numerous macrophages are also seen and present a formidable barrier to invading microorganisms. Fat cells appear singly or in clusters, and occasional mast cells are identified e
Edema
When a body region is inflamed, the areolar tissue in the area soaks up excess fluids like a sponge, and the affected area swells and becomes puffy
Connective tissue proper: loose connective tissue, areolar
-Description: Gel-like matrix with all three fiber types; fibroblasts, macrophages, mast cells, and some white blood cells
-Function: Wraps and cushions organs; its macrophages phagocytes bacteria; plays important role in inflammation; holds and conveys t
Adipose (Fat) Tissue
Nutrient storing ability is much greater. Adipocytes account for 90% of this tissue's mass. The matrix is scanty and the cells are packed closely together, giving a chicken-wire appearance to the tissue. Glistening oil droplet occupies most of fat cell's
Brown adipose tissue
Distinguished from the adipose tissue just described is sometimes called white fat or white adipose tissue. White fat stores nutrients (mainly for other cells), but brown fat contains abundant mitochondria, which use the lipid fuels to heat the bloodstrea
Reticular (loose) connective tissue*
Ressembles areolar connective tissue, but only fibers in its matrix are reticular fibers, which form a delicate network along which fibroblasts called reticular cells are scattered. Limited to certain sites
-Contains extracellular matrix
-Cleans out blood
Stroma
Supports many free blood cells (mostly lymphocytes) in lymph nodes, the spleen, and bone marrow
Connective tissue proper: loose connective tissue, adipose*
-Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet
-Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs
-Location:
Connective Tisse Proper-Dense Connective Tissues
Three varieties of dense connective tissue are dense regular, dense irregular, and elastic. They are fibrous connective tissues.
Dense Regular Connective Tissue*
Contains closely packed bundles of collagen fibers running in the same direction, parallel to the direction of pull. This arrangement results in white, flexible structures with great resistance to tension (pulling forcers) where the tension is exerted in
Connective tissue proper: dense connective, dense regular
-Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast
-Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one dir
Connective tissue Proper: Dense Irregular Connective Tissue*
Bundles of collagen fibers are much thicker and they are arranged irregularly; they run in more than one plane. Found on the dermis (skin) and forms fibrous joint capsules and the fibrous covering that surround some organs
-Description: Primarily irregula
CTP: Dense Elastic Connective Tissue*
-Few ligaments, such as those connecting adjacent vertebrae, are very elastic.
-Dense regular connective tissue
-Many of the larger arteries have stretchy sheets of elastic connective tissue in their walls
-Description: Dense regular connective tissue con
Cartilage
Stands on both tension and compression and has qualities intermediate between dense connective tissue and bone. It's tough but flexible, providing a resilient rigidity to the structures it supports.
-They lack nerve fibers and is avascular and receives nu
Chondroblasts
The predominant cell type in growing cartilage, produce new matrix until the skeleton stops growing at the end of adolescence
Chondrocytes
The firmness of the cartilage matrix prevents the cells from becoming widely separated or mature cartilage cells
Hyaline Cartilage
Most abundant cartilage in the body containing large numbers of collagen fibers, they are not apparent and the matrix appears glassy blue-white when viewed by the unaided eye*
-Gives support with some pilability and covers the end of long bones as articul
Cartilage: Elastic*
-Description: Has elastic fibers
-Do stain, semi-solid form of matrix
-Found where strength and exceptional stretchability are needed, elastic cartilage forms the "skeletons" of the external ear (the pinna) and the epiglottis (the flap that covers the ope
Cartilage: Fibrocartilage*
-Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate
-Function: Tensile strength allows it to absorb compressive shock
-Location: Intervertebral discs; public symphysis; discs of knee joint; spine
Bone osseous tissue
-Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized
-Function: Supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat;
Bone: Compact Bone
Central cannel are artery and veins
-Have circular tings of a bone
-Has lacuna that secrete out of cellular matrix
-Matrix: Hard, calcified
-Cells: Osteocytes in lacunae
Osteocytes
-Reside in the lacunae within the matrix they have made
-Osteons: A cross section of bone tissue reveals closely packed structural units formed of concentric rings of bony matrix (lamellae) surrounding central canals containing the blod vessels and nerves
Blood
-Connective tissue
-Description: Red and white blood cells in a fluid matrix (plasma)
~It develops from mesenchyme and consists of blood cells, surrounded by a non living fluid matrix
-Function: Transport respiratory gases, nutrients, wastes, and other su
Muscle tissue
Highly cellular, well-vascularized tissues that are responsible for most types of body movement
-Possess myofilaments, elaborate versions of the actin and myosin filaments that bring about movement or contraction in all cell types.
-Three types: skeletal,
Skeletal Muscle
-Description: Long, cylindrical, multinucleate cells; obvious striations
-Function: Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control
-Location: In skeletal muscles attached to bones or occasionally to s
Cardiac Muscle
-Description: Branching, striated, generally, uninucleate cells that interrogate at specialized junctions (intercalated discs: Branching cells that fit together tightly at unique junctions)
-Function: As it contracts, it propels blood into the circulation
Smooth Muscle
-Description: Spindle-shaped cells with central nuclei; no striations; cells arranged closely to form sheets
-Function: Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control
-Location: Mostly in the wall
Nervous Tissue
-Description: Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonexcitable supporting cells
-Function: Neurons transmit electrical signals from sensor
Neurons
Highly specialized nerve cells that generate and conduct nerve impulses
Covering and Lining Membranes
Three types: Cutaneous, mucous, or serous
-Composed of at least two primary tissue types: an epithelium bound to an underlying layer of connective tissue proper
Synovial membranes
Line joint cavities and consist of connective tissue only
Cutaneous Membrane
-Covers the body surface
-Consisting of a keratinized stratified squameous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis)
-Exposed of air and dry membrane
Mucous Membranes
-Line body cavities that are open to the exterior, such as the hollow organs of the digestive, respiratory, and urogenital tracts.
-They are wet or moist membranes bathed by secretions or in the case of the urinary mucosa, urine.
-Mucosa contain either st
Serous Membranes
-Lines body cavities that are closed to the exterior
-Moist membranes found in closed ventral body cavities
-Consists of simple squamous epithelium (mesothelium) resting on a thin layer of loose connective (areolar) tissue
-Mesothelial cells ass hyaluroni
Tissue Repair
When tissue is injured, these barriers are penetrated
-This stimulates the body's inflammatory and immune responses, which battles largely in the connective tissues of the body. Inflammatory response is a nonspecific reaction that develops quickly whereve
Regeneration
Replaces destroyed tissue with the same kind of tissue
Fibrosis
Connective tissue proliferates to form scar tissue
Steps of Tissue Repair: Step One
1) Inflammation sets the stage:
-Severed blood vessels bleed
-Inflammatory chemicals are released
-Local blood vessels become more permeable, allowing white blood cells, fluid, clotting proteins, and other plasma proteins to seep into the injured area
-Cl
Steps of Tissue Repair: Step Two*
2) Organization restores the blood supply:
-The clot is replaced by granulation tissue, which restores the vascular supply
-Fibroblasts produce collagen fibers that bridge the gap
-Macrophages phagocytize dead and dying cells and other debris
-Surface epi
Steps of Tissue Repair: Step Three
3) Regeneration and fibrosis effect permanent repair:
-The fibroses area matures and contracts; the epithelium thickens
-A fully regenerated epithelium with an underlying area of scar tissue results
Three primary germ layers
Epithelium arises from three primary germ layers ectoderm, mesoderm, and endoderm; muscle and connective tissue from mesoderm; nervous tissue from ectoderm
-Form the four primary tissues-epithelium, nervous tissue, muscle, and connective tissues-that make
Stratified squameous keratinized epithelium*
keratinized stratified squameous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis)
-Dermis: thick on back
-Extrameous Kemotosis: Cell signaling mechanism communicating to white blood cells (HELP!!)
-Epodermis: White blo