Histology W.U. : Using your medical dictionary, what do you think Histology is the study of?

Histology The study of different types of tissues Tissue: Cells working together in functionally related groups

Histology Separated into four major categories based on their function and the embryonic tissue of origin Tissue Function Embryonic Tissue Epithelial Cover & Protection Ectoderm, endoderm, and mesoderm Connective Support Mesoderm Muscle Movement & contraction Nervous Signaling & communication Ectoderm

Epithelial Tissue Location: Function: Lines nearly every cavity and surface of the human body Form glands Function: Protect the tissues they cover Regulate gas and nutrient exchange Secrete substances such as sweat, hormones, mucus, and enzymes Provide sensation with the environment

Epithelial Classification: First name of tissue indicates the number of layers Simple: One layer of cells Stratified: More than one layer of cells

Epithelial Classification Last name of tissue describes the SHAPE of cells Squamous: cells wider than tall Cubodial: cells are as wide as tall, as in “cubes” Columnar: cells are taller than they are wide, like columns

Epilthelial Put it all together… Special epithelial tissues Simple squamous Simple columnar Stratified cubodial Special epithelial tissues Pseudostratified Transitional

Epithelial Special characteristics: Cells are packed tightly together, forming a protective layer around organs High capacity for regeneration Produce fluids for lubricating tissues and organs Avascular: No capillaries that directly nourish the cells Cells get what they need through diffusion of nutrients through the basement membrane

Simple Squamous Epithelium Single layer of flat cells with disc-shaped nuclei Function: Passage of materials by passive diffusion and filtration Secrete lubricating substances in serosae

Simple Squamous Epithelium Location Renal corpuscles Alveoli of lungs Lining of heart, blood, and lymphatic vessels Lining of ventral body cavity

Simple Cuboidal Epithelium Single layer of cube-like cells with large, spherical nuclei Function: Secretion and absorption

Simple Cuboidal Epithelium Location: Kidney tubules Secretory portions of small glands Ovary and Thyroid follicles

Simple Columnar Epithelium Single layer of column-shaped cells with oval nuclei Some may have cilia Function: Absorption Secretion of mucus, enzymes, and other substances Ciliated type propels mucus or reproductive cells by ciliary action

Simple Columnar Location: Non-ciliated: lines digestive tract, gallbladder, ducts of some glands Ciliated form: lines small bronchi, uterine tubes, uterus

Connective Tissues Most abundant tissue type in the body Ex: blood, bone, cartilage, tendons, ligaments… Made up of fibers and extracellular components in the embedded in fluid Types of Connective Tissues Loose Connective Tissue Dense Connective Tissue Cartilage Other Tissues

Connective Tissue Function: Protect Store energy Transport Insulate Connect all body tissues

Loose Connective Tissue Areolar: Binds cells and fibers together, allows movement Found under skin, surrounds capillaries Adipose: Fat, stores nutrients, insulates, protects organs Found under skin, around kidneys, within abdomen Reticular: Allows for structure and flow of substances Found in lymph nodes, bone marrow, spleen Loose arrangement of collagen fibers

Dense Connective Tissue Regular: Make up tendon and ligaments, tightly organized bundles of collagen Found in tendons, ligaments, fascia around muscles Irregular: Make up the dermis, tight bundles of collagen that are unorganized Found in the dermis of skin, submucosa of digestive tract

Cartilage Hyaline: Elastic Provides support while still being pliable, most abundant form Found in the ends of long bones, nose, trachea, and larnyx Elastic Provides support while still able to stretch Supports external ear, epiglottis

Cartilage Fibrocartilage: Provides strong support and handles heavy pressure Found in intervertebral discs, pubic symphysis, discs of knee joints

Other Tissues… Bone Blood Support, hard tissue of collagen fibers and calcium surrounding osteocytes Blood Tissue that contains red blood cells, proteins, and plasma

Muscle Tissue Cells are extremely long and contain protein fibers capable of contracting Separated into 3 main types: Skeletal muscle tissue Smooth muscle tissue Cardiac muscle tissue

Skeletal Muscle Tissue Voluntary muscle Can be contracted voluntarily Function in movement and maintenance of posture Visible striations Makes up the muscles that are attached to our skeleton

Smooth Muscle Tissue Involuntary muscle Found in: Muscle does not contract voluntarily Lines most of the organs of the body No visible striations Found in: GI Tract Respiratory Tract Blood vessels Bladder Uterus

Cardiac Muscle Heart, extremely dense, strong tissue Involuntary Large number of mitochondria to provide energy for the continuous contracting of the heart Striated like muscle tissue

Nervous Tissue Found in the brain, spinal cord, and nerves Consists of 2 main cells Neurons Neuroglia cells Responsible for communication

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