Porth's Essentials of Pathophysiology, 4e

20

Cell and Tissue Function

U N I T 1

Classification of TissueTypes

TABLE 1-1

TissueType

Location

Epithelial Tissue Covering and lining of body surfaces Simple epithelium Squamous

Lining of blood vessels, body cavities, alveoli of lungs Collecting tubules of kidney; covering of ovaries

Cuboidal Columnar

Lining of intestine and gallbladder

Stratified epithelium Squamous keratinized Squamous nonkeratinized

Skin

Mucous membranes of mouth, esophagus, and vagina

Cuboidal Columnar Transitional

Ducts of sweat glands

Large ducts of salivary and mammary glands; also found in conjunctiva

Bladder, ureters, renal pelvis Tracheal and respiratory passages

Pseudostratified

Glandular

Endocrine Exocrine

Pituitary gland, thyroid gland, adrenal and other glands Sweat glands and glands in gastrointestinal tract

Neuroepithelium

Olfactory mucosa, retina, tongue

Reproductive epithelium

Seminiferous tubules of testis; cortical portion of ovary

ConnectiveTissue Embryonic connective tissue Mesenchymal

Embryonic mesoderm

Mucous

Umbilical cord (Wharton jelly)

Adult connective tissue Loose or areolar

Subcutaneous areas Tendons and ligaments

Dense regular Dense irregular

Dermis of skin

Adipose Reticular

Fat pads, subcutaneous layers

Framework of lymphoid organs, bone marrow, liver

Specialized connective tissue Bone

Long bones, flat bones

Cartilage

Tracheal rings, external ear, articular surfaces Blood cells, myeloid tissue (bone marrow)

Hematopoietic

MuscleTissue Skeletal

Skeletal muscles Heart muscles

Cardiac Smooth

Gastrointestinal tract, blood vessels, bronchi, bladder, and others

NervousTissue Neurons Supporting cells

Central and peripheral neurons and nerve fibers

Glial and ependymal cells in central nervous system; Schwann and satellite cells in peripheral nervous system

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Epithelial Tissue Epithelial tissue forms sheets that cover the body’s outer surface, line the internal surfaces, and form glandular tis- sue. Underneath all types of epithelial tissue is a fibrous extracellular layer, called the basement membrane , which serves to attach the epithelial cells to adjacent connective tissue and may serve other functions, such as providing a barrier against cancer cell invasion and contributing to the filtration function of the glomerulus. The cells that make up epithelium have three general characteristics: (1) they have three distinct surfaces: a free surface or apical surface, a lateral surface, and a basal surface; (2) they are closely apposed and joined by cell-to-cell adhesion molecules, which form special- ized cell junctions; and (3) their basal surface is attached

tissues is called cell differentiation , a process that is controlled by mechanisms that switch genes on and off (see Chapter 4). All of the approximately 200 different cells of the body can be classified into the four basic or primary tis- sue types: epithelial, connective, muscle, and nervous (Table 1-1). These basic tissue types are often described by their embryonic origin. The embryo is essentially a three-layered tubular structure (Fig. 1-13). The outer layer of the tube is called the ectoderm ; the middle layer, the mesoderm ; and the inner layer, the endoderm . All of the mature tissue types originate from these three cel- lular layers. Epithelium has its origin in all three embry- onic layers, connective tissue and muscle develop mainly from the mesoderm, and nervous tissue develops from the ectoderm.