TISSUES Tissue- a group of similar cells that perform a common function 1.Each type a.Performs at least 1 unique function to maintain homeostasis b.All tissues are found embedded in a matrix. (nonliving material) c.Matrix amounts change from tissue to tissue Histology - the study of tissue 4 Basic Tissue Types 1.Epithelial a.Covers and protects surfaces b.Lines cavities c.Moves substances in and out of blood (excrete, secrete, absorb) d.Form glands 2.Connective 3.Muscle a.Produce movement 4.Nervous a.Most complex b.Communicate bt. Body areas c.Controls the integration of activities Embryonic Development of Tissues 1.Tissue development - occurs 2 months after conception 2.Blastocyst - hollow ball of cells, that connect to uterus 3.At two weeks - blastocyst regroups into: a.3 germ layers i.Endoderm ii.Mesoderm iii.Ectoderm Gastrulation - the process when the blastocyst regroups into germ layers Histogenesis 1.The process of each germ layer differentiating into different tissue types Epithelial Tissue 2 types
Membranous & Glandular Membranous 1.Covers body and lines serous cavities 2.Lines blood & lymphatic vessels 3.Lines respiratory, digestive & genitourinary tracts Glandular 1.This tissue is grouped in a solid cord that forms secretory units of endocrine and exocrine glands Functions of Epithelial Tissue 1.Protection - most important (skin) 2.Sensory functions - found in nose, eyes and ears 3.Secretion - most important glandular function….hormones, mucus, digestive juice and sweat 4.Absorption - lines lungs and small intestine 5.Excretion - lines kidney and allows removal of urine from kidneys Epithelial tissue has little or no matrix. Epithelial tissue connects to underlying connective tissue by a permeable noncellular adhesive - basement membrane Both connective and epithelial tissue secrete a basement membrane made of glycoproteins. What makes the basement membrane? 1.Epithelial tissue - basal lamina (makes membrane) 2.Connective tissue - reticular lamina (makes membrane) 3.Epithelial tissue has no blood vessels - avascular 4.This tissue is held together depending on where the tissue is in the body by 3 types of cell junctions Desmosomes 1.Very strong, resist stretching 2.Like small “spot welds” they resemble Velcro 3.Hold cells together or to underlying basal lamina 4.Found in superficial layers of the skin Gap Junction 1.Form gaps or tunnels between two adjoining cells 2.This tunnel allows cytoplasmic materials to pass between both cells 3.This coordinates movements such as cilia in trachea Tight Junctions 1.Join cells by “collars” (similar to six pack) 2.Molecules cannot pass through this connection 3.Found in the lining of intestines
Classification by Shape and Layers 1.Squamous - flat and plate like 2.Cuboidal - cube-shaped 3.Columnar - rectangle shaped 4.