Tissues HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

WHAT ARE TISSUES? Groups of cells that are similar in structure and perform a common or related function Basic tissue types: Epithelial Connective Muscle Nervous Tissues are organized into organs such as kidneys and the heart Most organs contain all four tissue types The arrangement of the tissues determines the organ’s structure and capabilities

Epithelial Tissue Covers all body surfaces both inside and out Protects body from moisture loss, bacteria, and internal injury - Main glandular (glands) tissue. - Usually has no vascular tissue - blood supply - Cells reproduce rapidly (rapid healing). - Cells tightly packed together It takes about 27 days for the outer layer of skin to shed and be replaced; that works out to 1.5 pounds of skin cells per year.

Epithelial tissue Each epithelium has two names The first name indicates the number of cell layers present and the second describes the shape of its cells Simple = single layer Stratified = multiple layers Squamous = flat and scale-like Cuboidal = box-like Columnar = tall and column shaped

SIMPLE EPITHELIA Simple epithelia are most concerned with absorption, secretion, and filtration They are a single layer and usually very thin They do not function in protection

Simple Squamous Description: Single layer of flattened cells Tissue Description: Single layer of flattened cells Function: Diffusion and filtration in sites where protection is not important Location: Kidneys, air sacs, blood vessels, lymphatic vessels

Simple Cuboidal Description: Single layer of cube-like cells Function: Secretion and absorption Location: Kidney tubules, ducts, ovary surface

Simple Columnar Description: Single layer of tall cells; some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells) Function: Absorption; secretion of mucus, enzymes, and other substances; Ciliated type propels mucus by ciliary action Location: Nonciliated type lines most of the digestive tract; gall bladder; ciliated variety lines small bronchi and some regions of the uterus

Pseudostratified Columnar Description: Single layer of cells of differing heights, some not reaching the free surface; may contain mucus-secreting Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action Location: Nonciliated type in male’s sperm’carrying ducts; ciliated type lines the trachea and most of the upper respiratory tract

Stratified cuboidal epithelium

STRATIFIED EPITHELIA Stratified epithelia contain two or more cell layers They generate from below (basal cells divide and push apically to replace the older surface cells) Stratified epithelia are considerably more durable than simple epithelia Protection is their major (but not their only) function

Stratified Squamous Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar; surface cells are squamous; basal cells are active in mitosis and produce the cells of more superficial layers Function: Protects underlying tissues in areas subjected to abrasion Location: Moist linings of esophagus, mouth, and vagina; epidermis of the skin

Transitional Epithelium Description: Resembles both stratified squamous and stratified cuboidal; basal cells are cuboidal or columnar; surface cells are dome shaped or squamous-like depending on degree of organ stretch Function: Stretches readily, permits stored urine to distend urinary organ Location: Lines the ureters, bladder, and part of the urethra

GLANDULAR EPITHELIUM A gland consists of one or more cells that make and secrete a particular product This product, called a secretion, is a water-based fluid that usually contains proteins Glandular cells obtain needed substances from the blood and transform them chemically into a product that is then discharged from the cell There are two types of glands: endocrine (“internally secreting”) and exocrine (“externally secreting”) Endocrine glands (ductless glands) produce hormones Secrete hormones into extracellular space, where they will enter the blood and travel to target organs Exocrine glands secrete their products onto body surfaces or into body cavities

Glandular Epithelium Cells are specialized to produce and secrete substances They make up the GLANDS exocrine glands: salivary, sweat endocrine glands: hormones

THE ink of tattoos must be injected below the basement membrane  

Identify the tissues