Capter 4: Tissue: The Living Fabric

CT proper: loose connective tissues Reticular connective tissue

Resembles areolar tissue, but fibers are thinner reticular fibers Fibroblast cells are called reticular cells - Secrete reticular fibers made up of thin collagen Reticular fibers form a mesh-like stroma that acts as a support for blood cells in lymph nodes, spleen, and bone marrow

•CT proper: dense connective tissues Dense IRREGULAR connective tissue

Same elements as dense regular, but bundles of collagen are thicker and irregularly arranged, that, they run in all directions. Forms sheets rather than bundles where tension is exerted from many different directions Resists tension from many directions Found in: - Dermis - Fibrous joint capsules - Fibrous coverings of some organs

collagen fibers

Strongest and most abundant type Tough; provides high tensile strength (the ability to resist being pulled apart) to the matrix

dense regular connective tissue

Very high tensile strength; can withstand high tension and stretching Closely packed bundles of thick collagen fibers run parallel to direction of pull - Fibers appear as white structures • Great resistance to pulling - collagen fibers are slightly wavy, so stretch a little which allows the tissue to stretch a little Fibroblasts manufacture collagen fibers and ground substance Very few cells and ground substance, mostly fibers Poorly vascularized Example: tendons and ligaments

simple squamous epithelium

- Cells are flattened laterally, and cytoplasm is sparse - Function where filtration or the exchange of substances by rapid diffusion is a priority - Example: kidney, lungs

Pseudostratified columnar epithelium

- Cells vary in height and appear to be multi-layered and stratified, but tissue is in fact single-layered simple epithelium "Pseudo" means false Many cells are ciliated where it propel sheets of dust-trapping mucus away from the lungs. - Involved in secretion, particularly of mucus, and also in movement of mucus via ciliary sweeping action - Located mostly in upper respiratory tract, ducts of large glands, and tubules in testes

There are four main classes of connective tissue

- Connective tissue proper - Cartilage - Bone - Blood

4. Avascular, but innervated

- Contains no blood vessels, but supplied by nerve fibers. - nourished by substances diffusing from blood vessels in the underlying connective tissue.

Two special simple squamous epithelia are based on locations

- Endothelium: lining of lymphatic vessels, blood vessels, and heart - Mesothelium: serous membranes in the ventral body cavity and covering its organs.

Transitional Epithelium

- Forms lining of hollow urinary organs - Found in bladder, ureters, and urethra - Cells of its basal layer are cuboidal or columnar - Ability of cells to change shape when stretched allows for increased flow of urine and, in the case of bladder, more storage space

stratified epithelial tissue

- Involve two or more layers of cells - New cells regenerate from below Basal cells divide and migrate toward surface - More durable than simple epithelia because protection is the major role

elastic fibers

- Long, thin, elastic fibers form branching net-works in the extracellular matrix - contain elastin that allows for stretch and recoil like rubber bands. - found where greater elasticity is needed, for example, in the skin, lungs, and blood vessel walls.

stratified squamous epithelium

- Most widespread of 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. - Located in areas of high wear and tear (example: skin) - Keratinized cells found in skin; nonkeratinized cells are found in moist linings

Connective tissue proper subclass: loss connective tissue: Adipose (Fat) Tissue White Fat

- Similar to areolar tissue but greater nutrient storage (mainly for other cells) - Cells are called adipocytes - The matrix is scanty and the cells are packed closely together, giving a chicken-wire appearance to the tissue - richly vascularized, indicating its high metabolic activity - in subcutaneous tissue, it functions in shock absorption, insulation, and energy storage

there are three types of musle tissue

- Skeletal muscle - Cardiac muscle - Smooth muscle

Bone (aka osseous tissue)

- ability to support and protect body structures - Stores fat and synthesizes blood cells in cavities - similar to that of cartilage but is harder and more rigid and has more collagen - Has inorganic calcium salts (bone salts) - Osteoblasts produce the organic portion of the matrix, and then bone salts are deposited on and between the fibers. - osteocytes, reside in the lacunae within the matrix they have made - Osteons are concentric rings of bony matrix (lamellae) surrounding central canals containing the blood vessels and nerves serving the bone. - bone is well supplied by invading blood vessels.

simple cuboidal epithelium

- consists of a single layer of cells as tall as they are wide - Important functions are secretion and absorption. - forms the walls of the smallest ducts of glands and of many kidney tubules.

skeletal muscle tissue

- contraction is under our conscious control, skeletal muscle is often referred to as voluntary muscle - attached to the bones of the skeleton - as they contract they pull on bones or skin, causing body movements - its cells are called muscle fibers Contain multiple nuclei Appear striated or banded reflects the precise alignment of their myofilaments

cardiac muscle tissue

- found only in the walls of the heart - involuntary muscle - Like skeletal muscle cells, cardiac muscle cells are striated - uninucleate (one nucleus) with the nucleus situated centrally - Branching cells that fit together tightly at unique junctions called intercalated discs

5. Regeneration

- has a high regenerative capacity - If and when their apical-basal polarity and lateral contacts are destroyed, epithelial cells begin to reproduce themselves rapidly. As long as epithelial cells receive adequate nutrition, they can replace lost cells by cell division.

neurons

- highly specialized nerve cells that generate and conduct nerve impulses - they are branching cells with cytoplasmic extensions or processes that enable them to: ●Respond to stimuli (via processes called dendrites) ●Transmit electrical impulses over substantial distances within the body (via processes called axons)

Fibrocartilage

- intermediate between hyaline cartilage and dense regular connective tissues - Its rows of chondrocytes (a cartilage feature) alternate with rows of thick collagen fibers (characteristic of dense regular connec-tive tissue) - Because it resists both compression and tension well, fibrocartilage is found where strong support and the ability to withstand heavy pressure are required: for example, the intervertebral discs (resilient cushions between the bony vertebrae) and the spongy cartilages of the kn

smooth muscle tissue

- its cells have no visible striations - involuntary muscle - individual smooth muscle cells are spindle shaped with one nucleus - found mainly in the walls of hollow organs other than the heart (digestive and urinary tract organs, uterus, and blood vessels) - It squeezes substances through these organs by alternately contracting and relaxing.

elastic cartilage

- nearly identical to hyaline cartilage - has many more elastic fibers - Found in ears and epiglottis

Stratified columnar epithelium

- rare - Small amounts found in pharynx, in male urethra, and lining some glandular ducts - Usually occurs at transition areas between two other types of epithelia - Only its apical layer of cells is columnar.

stratified cuboidal epithelium

- rare in the body - mostly found in the ducts of some of the larger glands (sweat glands, mammary glands). It typically has two layers of cuboidal cells.

reticular fiber

- short, fine fibers are made of a different type of collagen than the more common, thicker collagen fibers - They connect to the coarser collagen fibers, but they branch extensively, forming delicate networks that surround small blood vessels and support the soft tissue of organs. -They are particularly abundant in the basement membrane of epithelial tissues, and around capillaries, where they form fuzzy "nets" that allow more stretch than the larger collagen fibers.

simple columnar epithelium

- single layer of tall, closely packed cells Some cells have microvilli, and some have cilia Some layers contain mucus-secreting goblet cells - Involved in absorption and secretion of mucus, enzymes, and other substances Ciliated cells move mucus - Found in digestive tract (from the stomach through the rectum), gallbladder, ducts of some glands, bronchi, and uterine tubes the digestive tract lining has two distinct modifications that make it ideal for that dual function: ●Dense microvilli on the apical surface of absorptive cells ●Tubular glands made primarily of cells that secrete mucus-containing intestinal juice

catilage

- stands up to both tension and compression - matrix secreted from chondroblasts (during growth) and chondrocytes (adults) ~Chondrocytes found in cavities called lacunae - It is tough but flexible, providing a resilient rigidity to the structures it supports. ~ cartilage is up to 80% water, with packed collagen fibers and sugar proteins (chondroitin and hyaluronic acid) - lacks nerve fibers - Avascular: receives nutrients by diffusion from membrane surrounding it (perichondrium) Periochondrium gives rise to chondroblasts and chondrocytes

Three types of connective tissue fibers provide

- support 1. Collagen fibers 2. elastic fibers 3. reticular fibers

Hyaline cartilage or gristle

- the most abundant cartilage in the body - it contains large numbers of collagen fibers, they are not apparent and the matrix appears glassy (hyal = glass, transparent) blue-white when viewed by the unaided eye. - Hyaline cartilage provides firm support with some pliability - Found at tips of long bones, nose, trachea, larynx, and cartilage of the ribs

Blood

- the most atypical con-nective tissue because it is fluid - classified as a connective tissue because it develops from mesenchyme and consists of blood cells, surrounded by a nonliving fluid matrix called blood plasma - Red blood cells are most common cell type - Also contains white blood cells and platelets - Fibers are soluble proteins that precipitate during blood clotting - Functions in transport vehicle in the cardiovascular system, carrying nutrients, wastes, respiratory gases, and other substances

Connective tissue proper subclass: loss connective tissue: Areolar Connective Tissue

- the most widely distributed connective tissue in the body - it serves as a universal packing material between other tissues - Contains fibroblasts that secrete loose arrangement of mostly collagen fibers - It binds body parts together while allowing them to move freely over one another - Loose fibers allow for increased ground substance, which can act as water reservoir by holding more interstitial fluid

epithelium's second name describes

- the shape of its cells - vary in heights

muscle tissue

- well-vascularized tissues that are responsible for most types of body movement - Muscle cells possess myofilaments made up of actin and myosin proteins that bring about contraction

Epethelial tissue has two main form

1. Covering and lining epithelim 2. Glandular epithelium

Connective Tissue Proper: Dense connective tissue has three varieties:

1. Dense regular 2. Dense irregular 3. Elastic

Glands are classified according to two sets of traits

1. Endocrine: internally secreting (example: hormones) 2. Exocrine: externally secreting (example: sweat)

There are three types of cartilage:

1. Hyaline cartilage 2. Fibrocartilage 3. Elastic cartilage

Epithelial tissue has five distinguishing characteristics:

1. Polarity 2. Specialized contacts 3. Supported by connective tissues 4. Avascular, but innervated 5. Regeneration

the basement membrane consists of two layers:

1. basal lamina 2. reticular lamina. Deep to basal lamina Consists of network of collagen fibers

Connective tissues three characteristics that together set them apart from other primary tissues

1. cells are suspended/embedded in extracellular matrix (ECM) - supports cells so they can bear weight, withstand tension, endure abuse 2. all have common embryonic origin - All connective tissues arise from mesenchyme (an embryonic tissue). 3. Have varying degrees of vascularity (cartilage is avascular, bone is highly vascularized)

All connective tissues have three main elements

1. ground substance 2. fibers 3. cells - Composition and arrangement of these three elements vary considerably in different types of connective tissues

ground substance has three components

1. interstitial fluid 2. cell adhesion proteins ("glue" fpr attachment) 3. proteoglycans (sugar proteins), made up of protein core + large polysaccharides - Example: chrondroitin sulfate and hyaluronic acid Water also is trapped in varying amounts, affecting viscosity of ground substance

Connective tissue proper has two subclasses

1. loose connective tissue (areolar, adipose, and reticular) 2. dense connective tissue (dense regular, dense irregular, and elastic)

CT proper: dense connective tissues Elastic connective tissue

A few ligaments, such as those connecting adjacent vertebrae, are very elastic. many of the larger arteries have stretchy sheets of elastic connective tissue in their walls - Arteries need to stretch when blood enters and recoil to push blood out

Connective tissue is also home to an assortment of other cell types, such as:

Adipocytes (fat cells), white blood cells (WBC), mast cells, and macrophages.

3. Supported by connective tissues

All epithelial sheets are supported by connective tissue. in between the epithelial and connective tissues is a basement membrane that reinforces: - the epithelial sheet, - helps it resist stretching and tearing, and -defines the epithelial boundary.

Clinical - Homeostatic Imbalance 4.1

An important characteristic of cancerous epithelial cells is their failure to respect the basement membrane boundary, which they penetrate to invade the tissues beneath - Cancerous epithelial cells are not contained by the basement membrane boundary like other cells - They penetrate the boundary and invade underlying tissues, resulting in spread of cancer

All epithelial tissues have two names (first and last name)

First name indicates number of cell layers Simple epithelia are a single layer thick Stratified epithelia are two or more layers thick and involved in protection (example: skin)

Each major class of connective tissue has a resident cell type that exists in immature (-blast) and mature (-cyte) forms - less active form of "blast" cell that now becomes part of and helps maintain health of matrix

For example: ● Fibroblasts in connective tissue proper become fibrocytes. ●Chondroblasts in cartilage become chondrocytes. ●Osteoblasts in bone become osteocytes. hematopoietic stem cells in bone marroe

Mast cells: chemicals include:

Heparin - an anticoagulant chemical that prevents blood clotting when free in the bloodstream (but in human mast cells it appears to regulate the action of other mast cell chemicals) • Histamine - a substance that makes capillaries leaky

Macrophages

Phagocytic cells that "eat" dead cells, microorganisms; function in immune system peppered throughout loose connective tissue, bone marrow, and lymphoid tissue

glandular epithelia

Secretory tissue in glands (example: salivary glands)

interstitial fluid

The ground substance consists of large amounts of fluid and functions as a molecular sieve through which nutrients and other dissolved substances can diffuse between the blood capillaries and the cells. The fibers embedded in the ground substance make it less pliable and hinder diffusion somewhat

unicellular (one-celled) exocrine gland

The only important examples are mucous cells and goblet cells. sprinkled in the epithelial linings of the intestinal and respiratory tracts

cell adhesion proteins (CAMs)

These proteins serve mainly as a connective tissue glue that allows connective tissue cells to attach to the extracellular matrix.

Relative number of cells forming the gland

Unicellular (example: goblet cells) or multicellular (example: salivary)

Epithelial tissue (epithelium)

a sheet of cells that covers a body surface or lines a body cavity

Connective tissue is the most

abundant and widely distributed of primary tissues

The immature (-blast) cells are

actively mitotic secretes the ground substance and the fibers characteristic of their particular matrix. Once they synthesize the matrix, the blast cells assume their mature, less active -cyte form.

1. Polarity

all epithelia have two surfaces that differ in structure and function: apical and basal surface.

multicellular exocrine glands have two basic parts:

an epithelium-derived duct and a secretory unit (acinus) consisting of secretory cells

simple epithelia

are most concerned with absorption, secretion, and filtration. Because they consist of a single cell layer and are usually very thin, protection is not one of their specialties.

basal surface

attached to the underlying connective tissue a thin supporting sheet called the basal lamina ~ consists largely of glycoproteins secreted by the epithelial cells plus some fine collagen fibers.

One noticeable difference between different types of connective tissue is how richly they are supplied by blood vessels. Cartilage is __________. Dense connective tissue is ____________. and the other types of connective tissue have a ______________.

avascular. poorly vascularized, rich supply of blood vessels.

Major functions of connective tissue:

binding and support, protecting, insulating, storing reserve fuel, and transporting substances (blood) For example, bone and cartilage support and protect body organs by providing the hard underpinnings of the skeleton. Fat insulates and protects body organs and provides a fuel reserve. Blood transports sub-stances inside the body.

Proteoglycans

consist of a protein core to which large polysaccharides called glycosaminoglycans (GAGs) are attached. The strand-like GAGs [e.g., chondroitin sulfate and hyaluronic acid (hi0ah-lu-ron9ik)] stick out from the protein core like the fibers of a bottle brush. tend to form huge aggregates in which the GAGs intertwine and trap water forming a substance that varies from a fluid to a viscous gel. The higher the GAG content, the more viscous the ground substance

Connective tissue proper subclass: loss connective tissue: Adipose (Fat) Tissue Brown Fat

contains abundant mitochondria that use the lipid fuels to generate heat (instead of generating ATP molecules). - The bloodstream then carries this heat to warm the rest of the body

nervous tissue

controls

epithelial tissues

covers

2. Specialized contacts

epithelial cells fit closely together to form continuous sheets the sides of adjacent cells are tied together by tight junctions (prevent substances from leaking thorugh spaces between cells) and desmosomes (keeps cells from pulling apart).

the basic tissues are

epithelial, connective, muscle, and nervous tissue.

connective tissues consist largely of non-living

extracellular matrix, which separates, often widely, the living cells of the tissue matrix (womb) Because of its matrix, connective tissue can bear weight, withstand great tension, and endure abuses, such as physical trauma and abrasion, that no other tissue can tolerate.

Covering and lining epithelium (on external and internal surfaces (example: skin)

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 Epithelia: A _______ consists of one or more cells that make and secretes ________, an aqueous (water-based) fluid that usually contains proteins.

gland; secretion

In _______________, accumulating mucin distends the top of the cell, making the cells look like a glass with a stem (which is why it is named "goblet" cell

goblet cells

Together _____________ and __________ make up the extracellular matrix

ground substance and fibers

endocrine gland produce

hormones, a chemical messengers that they secrete by exocytosis directly into the extracellular space. From there the hormones enter the blood or lymphatic fluid and travel to specific target organs. Each hormone prompts its target organ(s) to respond in some characteristic way.

white blood cells or leukocytes

including neutrophils, eosinophils, and lymphocytes and other cell types that are concerned with tissue response to injury.

Mesenchyme

mature connective tissues arise from a common embryonic tissue

muscle tissue

moves

all such glands produce _________, a complex glycoprotein that dissolves in water when secreted.

mucin Once dissolved, mucin forms mucus, a slimy coating that protects and lubricates surfaces.

nervous tissue contains two major cell types

neurons and supporting cells

apical surface

not attached to surrounding tissue and is exposed to either the outside of the body or the cavity of an internal organ Most are smooth and slick SOME have specialized fingerlike projections called microvilli

simple epithelia

one layer of cells - found where absorption, secretion, and filtration occur a thin epithelial barrier is desirable.

main function of epithelial tissue

protection, absorption, filtration, excretion, secretion, and sensory reception

exocrine glands

secrete their products onto body surfaces (skin) or into body cavities. The unicellular glands do so directly (by exocytosis). the multicellular glands do so via an epithelium-walled duct that transports the secretion to the epithelial surface. diverse: they include the liver (which secretes bile); the pancreas (which synthesizes digestive enzymes); mucous, sweat, oil, and salivary glands; and many others.

Adipocytes

store energy as fat store nutrients

histology

study of tissues; complements the study of gross anatomy

connective tissue

supports

endocrine glands lose

their ducts during development

stratified epithelia

two or more layers of cells - common in high-abrasion areas where protection is important, such as the skin surface and the lining of the mouth

ground substance

unstructured gel-like material that fills the space between the cells and contains the fibers

mast cells

which typically cluster along blood vessels. These oval cells detect foreign microorganisms (e.g., bacteria, fungi) and initiate local inflammatory responses against them. Mast cell cytoplasm contains secretory granules (mast = stuffed full of granules) with chemicals that mediate inflammation, especially in severe allergies.

Clinical - Homeostatic Imbalance 4.2

• Avascular cartilage loses ability to divide as we age, so injuries heal slowly - Common in people with sports injuries • Later in life, cartilage can calcify or ossify (become bony), causing chondrocytes to die when poorly nourished

nervous tissue

• Main component of nervous system (brain, spinal cord, nerves) - Regulates and controls body functions

there are three common shapes of epithelial cells

● Squamous cells are flattened and scale-like ● Cuboidal cells are boxlike, approximately as tall as they are wide. ● Columnar cells are tall and column shaped.

aeorlar connective tissue functions

● Supporting and binding other tissues (the job of the fibers) ● Holding body fluids (the ground substance's role) ~ Essentially all body cells obtain their nutrients from and release their wastes into this "tissue fluid." ● Defending against infection (via the activity of white blood cells and macrophages) ●Storing nutrients as fat in adipocytes (fat cells)

With its enormous tensile strength, dense regular connective tissue forms:

● Tendons are cords that attach muscles to bones. ●Aponeuroses are flat, sheet-like tendons that attach muscles to other muscles or to bones. ● Ligaments bind bones together at joints. They contain more elastic fibers than tendons and are slightly more stretchy.