A connective tissue characterized by the presence of large numbers of adipocytes ( fat cells). It occurs subcutaneously, in the medullary cavities of bones, and elsewhere, serving as a stored source of body energy.
A secretory mode of glandular epithelium in which parts of the cells physically break away to form the secretory product.
A liquid connective tissue. It is the only body liquid with a cell concentration high enough to deserve the label "tissue".
Bone Marrow Tissue
The major material occupying the medullary cavities of bones. It is a subtype of connective tissue and is red when actively hemopoietic, yellow when it contains a high population of adipocytes, and gelatinous when it involutes with senility.
A mineralized subtype of connective tissue. It is the only body material routinely mineralized except for the enamel, dentin and cementum of teeth, and it forms a major structural component of (the organs called) bones.
A connective tissue with a firm but typically unmineralized extracellular matrix. It is also divided into three subtypes based primarily on the major type of proteinaceous fibers found in the matrix; elastic cartilage( elastic fibers), fibrocartilage ( collagenous fibers ) , and hyaline cartilage ( reticular fibers).
Connective Tissue Proper (fibrous connective tissue)
One of several subtypes of connective tissue. It is the most widely distributed connective tissue and forms part of every organ.
The material outside of and between cells. In many tissues it includes various types of proteinaceous fibers as well as amorphous protein/polysacchride material called ground substance.
A term used in various contexts to mean a muscle cell, a neuronal process or a protein component of the extracellular matrix. Proteinaceous extracellular fibers include those composed of elastin, collagen, and reticulin.
Epithelium that is specialized for secretion. Most is concentrated in the secretory organs called glands but are also scattered in the surface of mucous membranes as well.
The protein/polysaccharide component (glue) of the extracellular matrix. The polysaccharide portion is often formed by polymers of chondroitin sulfate, keratin sulfate, and hyaluronic acid.
Membranous Epithelium (surface epithelium)
The tissue that forms all outer surfaces of the body and lines all of its lumina and cavities. It is classified according to the shape of the surface cells ( squamous, cuboidal, columnar) and whether it is one cell thick or more than one cell thick.
Primitive connective tissue containing a large population of undifferentiated (stem) cells. It is concentrated in the nucleus pulposus of intervertebral discs and small amounts are present in the loose connective tissue around vessels.
The basic tissue functionally specialized for contraction. Three subtypes exist; skeletal (voluntary and striated), smooth (involuntary and not striated) and cardiac ( involuntary and striated).
Neuroglial Cell (glial cell)
A collective term encompassing the several types of support cells of the nervous system. They do not transmit impulses, but they support neurons physically and metabolically.
Neuron (nerve cell)
A cell specialized for impulse transmission. They are comprised of a single axon and one or more processes called dendrites.
Primary Germ Layer
Any of three defined strata that are formed during embryonic gastrulation: ectoderm, mesoderm, and endoderm. These germ layers differentiate to form the various tissues.
Cells of muscle tissue. they contain specialized organelles called myofibrils that shorten to initiate the contractile process.
Skeletal Muscle Tissue
Found in the skeletal muscles and in the wall of the esophagus. It's cells are cylindrical, multinucleated and under conscious voluntary control of the nervous system.
Cardiac Muscle Tissue
Found in the heart and in some of the large vessels near the heart ( aorta, pulmonary trunk, and some of their branches), It's cells are branched with single nuclei and it cannot be consciously controlled by the nervous system.
Smooth Muscle Tissue
Widely distributed and found within the walls of vessels and visceral organs, at the base of hair follicles and within the eyeball. Its cells are fusiform with single nuclei and like cardiac muscle, cannot be consciously controlled by the nervous system.
Caused by the cross linking of contractile proteins (myofilaments) in skeletal and cardiac muscle tissue.
A protein/polysaccharide material that the cells secrete, membranous epithelium sit on this thin amorphous structure.
Simple Epithelium ( squamous, cuboidal, columnar)
A single layer of cells ( squamous, cuboidal, columnar).
Stratified squamous epithelium
Dozens of cells thick with cuboidal cells near the basement membrane and squamous cells near the free surface.
Cuboidal cells, several cells thick but all cells touch the basement membrane.
Ciliated pseudostratified columnar epithelium
Tall columnar cells adjacent to shorter columnar cells and appears stratified but is not.
Exocrine Glandular Epithelium
Secretes its products onto free body surface ( either directly or through a duct).
Endocrine Glandular Epithelium
Secretes its products directly into the blood stream usually hormones or other chemical regulators.
An organ in which the functional tissue (parenchyma) is glandular epithelium. Usually it is in the form of a capsule.
Merocrine Secretion (eccrine secretion)
Involves exocytosis of secretory products with little or no visible change in the secretory cell appearance. This is utilized by the endocrine glands and some exocrine glands.
Process of sloughing dead glandular cells. These dead cells form the actual secretion in sebaceous (oil) glands.
Sensory neurons which carry impulses into the brain and spinal cord. They have a single axon and a cell body offset between the axon and the dendrite.
In the central nervous system, envelops the axons of the neurons to form myelin sheaths which speed up impulse conduction.
In the peripheral nervous system, envelope the axons of neurons to form myelin sheaths that speed up conduction of nerve impulses.
The characteristic cell of fibrous connective tissue and manufactures copious quantities of extracellular fibers and ground substance.
Bone cells located in tiny cavities called osseous lacunae. They are formed by osteoblasts that become trapped in the osseous lacunae.
Collagenous fiber and ground substance mixture that manufactures the matrix that forms the osseous lacunae.
Calcium phosphate salts from the interstitial fluid precipitate down onto the collagenous fibers to mineralize the osteoid in layers.
Found on articular surfaces within the costal cartilages of the ribs, and immature bones.
Found mainly in the aural and laryngeal cartilages. The predominant fibers are elastic fibers.
Found in intervertebral discs, articular discs, menisci and a few other loci, formed predominately of collagenous fibers.
Low in muscle and nerve tissue and high in epithelial and connective tissue. The ability of tissue or cells to regenerate.
Results from the proliferation of connective tissue proper after an injury in skin and other structures.