Histology Lecture 4

Key Points: Tissues Development of Epithelial Tissues Embryonic Development Epithelial Tissues Types Characteristics Classification Glandular Epithelia

Tissues Tissue = woven fabric Histology – Study of Tissues Microscopy Staining of Samples Cells of similar in structure and perform common or related functions Types of Tissues: Epithelial Connective Muscle Nervous

Primary Embryonic Germ Layers The 3 germ layers - the ectoderm, the mesoderm, and the entoderm (endoderm)

Primary Embryonic Germ Layers THE ECTODERM gives rise to the central nervous system; the peripheral nervous system; the sensory epithelia of the eye, ear, and nose; the epidermis and its appendages (the nails and hair); the mammary glands; the hypophysis; the subcutaneous glands; and the enamel of the teeth

Primary Embryonic Germ Layers THE MESODERM gives rise to connective tissue, cartilage, and bone; striated and smooth muscles; the heart walls, blood and lymph vessels and cells; the kidneys; the gonads (ovaries and testes) and genital ducts; the serous membranes lining the body cavities; the spleen; and the suprarenal (adrenal) cortices

Primary Embryonic Germ Layers THE ENTODERM gives rise to the epithelial lining of the gastrointestinal and respiratory tracts; the parenchyma of the tonsils, the liver, the thymus, the thyroid, the parathyroids, and the pancreas; the epithelial lining of the urinary bladder and urethra; and the epithelial lining of the tympanic cavity, tympanic antrum, and auditory tube

Sheet (or fabric) of cells that covers a body surface or lines a cavity. Two Types of Epithelium Covering and Lining Glandular Functions Form Boundaries Protection Absorption Filtration Excretion Secretion Sensory Reception Epithelium Tissue https://upload.wikimedia.org/wikipedia/commons/8/8f/Illu_epithelium.jpg https://anatomyeshs.wikispaces.com/file/view/glandular-epithelium-tissue.jpeg/111521505/glandular-epithelium-tissue.jpeg

Epithelium Tissue 5 Characteristics Polarity Specialized Contacts Two surfaces with different functions Apical Surface – Free upper surface Basal Surface – Lower Attached Surface Examples Microvilli – fingerlike projections of the plasma membrane increasing surface area Basal lamina – made of glycoproteins secreted by epithelial cells. It is a selective filter. Specialized Contacts Cells fit closely together to form specialized sheets with special contacts between the cells. Lateral Contacts – Tight Junctions/Desmosomes bind adjacent cells.

Epithelium Tissue 5 Characteristics 3. Supported by Connective Tissue All epithelial sheets rest on and are supported by connective tissue. Avascular but Innervated No blood vessels Receive nutrients from the blood vessels of the underlying tissue Regeneration Has a high regenerative capacity

Classification of Epithelial Tissue Simple Epithelia – consist of a single layer. Function – Absorption, secretion, and filtration Stratified Epithelia – composed of two or more single layers staked upon each other. Function – Protection. Examples skin and lining of the mouth. Squamous Cells – Flattened Cells Cuboidal Cells – Boxlike Columnar – Tall and Column Shape

Glandular Epithelia Gland – Consists of one or more cells that secrete a particular product. Secretion – An aqueous solution usually of proteins but may vary.

Glandular Epithelia Endocrine Glands Exocrine Glands They are ductless and secrete hormones. Exocrine Glands Secrete their productions onto a surface or body cavity.

Summary: Write a summary of your notes. List the things/items you feel are important. Paraphrase key topics Minimum of 10 Sentences Then exchange your summary with a neighbor. Read your neighbor’s summary. Return the summary. Compare your summary to your neighbor’s and update yours. Turn it in before you leave.