0. 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.

1. 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

2. 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.

3. 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

4. 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

5. 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

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

7. 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

8. 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

9. Stratified cuboidal epithelium

10. 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

11. 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

12. 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

13. 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

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

15. THE ink of tattoos must be injected below the basement membrane

21. Identify the tissues