1. Organized groups of cells that are similar in structure and function
Tissues
Organized groups of cells that are similar in structure and function

2. Tissues Tissues are organized into organs.
Organs can contain more than one type
Four main types:
Epithelial Tissue
Connective Tissue
Muscle Tissue
Nervous Tissue

3. Epithelial Tissue Also called epithelium (epithe = covering)
Lining, covering, and glandular tissue of body
Functions include protection, absorption, filtration, and secretion
Special Properties:
Avascular
Reproduce rapidly
Packed together tightly

4. Epithelial Tissues Each epithelium has two names:
One signifies the number of cell layers :
simple epithelium (one layer of cells)
stratified epithelium (more than one layer)
The second name describes the shape of its cells
Squamous cells (flattened like fish scales)
Cuboidal cells (cube-shaped like dice)
Columnar cells (shaped like columns)

5. Simple squamous epithelium
Single layer
Thin squamous cells resting on basement membrane
Forms serous membranes that line the body cavity
In air sacs of lungs

6. Simple cuboidal epithelium
Single layer
Cuboidal cells resting on basement membrane
Common in glands and ducts
Forms walls of kidney tubules

7. Simple columnar epithelium
Single layer
Columnar cells
Goblet cells that secrete mucus are in this layer
Lines digestive tract
Mucous membranes that line body cavities

8. Pseudostratified Columnar Epithelium
Vary in height so false impression that stratified
Functions in secretion and absorption
Lines respiratory tract

9. Stratified squamous epithelium
Most common stratified epithelium
Found in areas that receive friction, like esophagus, mouth, and skin

10. Transitional Epithelium
Highly modified stratified squamous epithelium
Forms lining of urinary bladder, ureter, and urethra
Basal layer = columnar / cuboidal
When organ is distended (stretched) with urine, the cells flatten and become squamous-like
Allows ureter wall to stretch with greater volumes of urine

11. Glandular Epithelium
Gland – one or more cells that make and secrete a product
Secretion – product of gland that contains proteins in aqueous solution
Endocrine gland – ductless, diffuse secretion (hormones) directly into the blood (ex: thyroid, adrenal, pituitary glands)
Exocrine gland – retain ducts, secretions empty through ducts to epithelial surface (ex: sweat glands, liver, pancreas)

12. Connective Tissue Connects body parts
Most abundant and widely distributed tissue
Functions include protecting, supporting, and binding together other tissues
Well vascularized (exceptions tendons, ligaments; cartilage is avascular)
Connective tissues includes cells plus extracellular matrix – nonliving substance outside cells

13. Extracellular Matrix
Produced by connective tissue and secreted to exterior
Ground substance composed largely of water and proteins
Cell adhesion proteins allow connective tissue cells to attach to matrix fibers
The following types of connective tissue are discussed in order of most rigid to softest

14. Bone
Bone – osseus tissue, composed of bone cells in cavities called lacunae, surrounded by hard matrix of calcium salts and collagen fibers
Protects and supports body organs

15. Cartilage Less hard and more flexible than bone
Chondrocyte – mature cartilage cell
Hyaline cartilage – most widespread
Abundant collagen fibers in a matrix with glassy appearance (hyalin = glass)
Forms larynx, connects ribs to sternum, covers bones to form joints
Fetus skeleton made of hyaline cartilage

16. Hyaline Cartilage

17. Fibrocartilage
Highly compressible
Forms disks between vertebrae

18. Elastic Cartilage Found in a structure with elasticity
Supports external ear

19. Dense Connective Tissue
Also called dense fibrous tissue
Collagen fibers as main matrix element
Fibroblasts – fiber forming cells between collagen fibers
Two types:
Tendons – connect skeletal muscles to bones
Ligaments – connect bones to bones at joints
Ligaments more stretchy (more elastic fibers) than tendons

20. Dense Fibrous Tissue

21. Loose Connective Tissue
Softer, fewer fibers and more cells than other connective tissues except blood
Areolar tissue – most widely distributed connective tissue
Soft, pliable, “cobweb”-like tissue
Cushions and protects body organs it wraps
Provides reservoir of water and salts for surrounding tissue
site where nutrients are obtained and wastes released

22. Areolar Tissue

23. Loose Connective Tissue
Adipose Tissue – commonly called fat
Areolar tissue in which fat cells predominate
Insulates body and protects it from extreme T
Stored in body and cushions some organs

24. Adipose Tissue
Oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side

25. Blood
Blood – vascular tissue; consists of blood cells surrounded by a matrix called blood plasma
Atypical connective tissue
Transport vehicle for cardiovascular system

27. Muscle Tissue
Muscle tissues are highly specialized to contract or shorten to produce movement

28. Skeletal Muscle
Skeletal muscle tissue – skeletal muscle organs connected to the skeleton.
Controlled voluntarily
Form flesh of the body – muscular system
Contraction leads to pulling on bone or skin
Result is movement or changes in expression
Cells are long, cylindrical, multinucleate, and have obvious striations

29. Skeletal Muscle Long Cylindrical Multinucleate Striations
Called “muscle fibers”

30. Cardiac Muscle Found only in the heart
Contractions lead to propelling of blood through the blood vessels
Cardiac muscle cells are uninucleate, short, branching with striations and fit tightly together at intercalated disks
Gap junctions with ion flow
Involuntarily controlled

31. Cardiac Muscle Cells short Striated Branching Uninucleate
Intercalated Discs

32. Smooth Muscle
Smooth muscle (Visceral Muscle) – found in walls of hollow organs (stomach, uterus, blood vessels, etc.)
Contractions lead to the organ constricting or dilating so substances are propelled
No striations, uninucleate, spindle-shaped

33. Smooth Muscle
No striations
Uninucleate
Pointed ends (spindle shaped)

34. Nervous Tissue Nervous Tissue – made of cells called neurons
Neurons receive and conduct electrochemical impulses from one part of body to another
Neurons and supporting cells (insulate and protect neurons) make up the nervous system: the brain, spinal chord, and nerves
Cytoplasm drawn out in extensions allows neurons to conduct impulses long distances

35. Neuron
Neurons in human hippocampus