2. 4-2
Tissues and Histology
• Tissue Level of Organization
– Epithelial
– Connective
– Muscle
– Nervous
• Histology: Microscopic Study of Tissues
3. 4-3
Embryonic Tissue
• Germ layers
– Endoderm
• Inner layer
• Forms lining of digestive tract and derivatives
– Mesoderm
• Middle layer
• Forms tissues as muscle, bone, blood vessels
– Ectoderm
• Outer layer
• Forms skin and neuroectoderm
4. 4-4
Epithelium Characteristics
• Consists almost entirely
of cells
• Covers body surfaces
and forms glands
• Has free and basal
surface
• Specialized cell contacts
• Avascular
• Undergoes mitosis
5. 4-5
Functions of Epithelia
• Protecting underlying structures
• Acting as barriers
• Permitting the passage of substances
• Secreting substances
• Absorbing substances
6. 4-6
Classification of Epithelium
• Simple
– Squamous, cuboidal, columnar
• Stratified
– Squamous, cuboidal, columnar
• Pseudostratified
– columnar
• Transitional
– Cuboidal to columnar when not stretched and
squamouslike when stretched
21. 4-21
Functions of Connective Tissue
• Enclosing and separating as capsules around
organs
• Connecting tissues to one another as tendons
and ligaments
• Supporting and moving as bones
• Storing as fat
• Cushioning and insulating as fat
• Transporting as blood
• Protecting as cells of the immune system
22. 4-22
Connective Tissue Cells
• Specialized cells produce the extracellular matrix
– Suffixes
• -blasts: create the matrix
• -cytes: maintain the matrix
• -clasts: break the matrix down for remodeling
• Adipose or fat cells
• Mast cells that contain heparin and histamine
• White blood cells that respond to injury or
infection
• Macrophages that phagocytize or provide
protection
• Stem cells
23. 4-23
Extracellular Matrix
• Components
– Protein fibers
• Collagen which is most common protein in body
• Reticular fill spaces between tissues and organs
• Elastic returns to its original shape after distension or
compression
– Ground substance
• Shapeless background
– Fluid
24. 4-24
Connective Tissue Categories
• Embryonic or mesenchyme
• Adult
– Loose
– Dense
– Connective tissue with special properties
– Cartilage
– Bone
– Blood
25. 4-25
Loose Connective Tissue
• Also known as areolar tissue
• Loose packing material of most organs and tissues
• Attaches skin to underlying tissues
• Contains collagen, reticular, elastic fibers and variety of cells
26. 4-26
Dense Connective Tissue
• Dense regular
– Has abundant collagen fibers
• Tendons: Connect muscles to bones
• Ligaments: Connect bones to bones
• Dense regular elastic
• Ligaments in vocal folds
• Dense irregular
• Scars
• Dense irregular collagenous
• Forms most of skin dermis
• Dense irregular elastic
• In walls of elastic arteries
29. 4-29
Connective Tissue with Special
Properties
• Adipose tissue
– Consists of adipocytes
– Types
• Yellow (white)
– most abundant, white at birth and yellows with age
• Brown
– found only in specific areas of body as axillae, neck and near
kidneys
• Reticular tissue
– Forms framework of lymphatic tissue
– Characterized by network of fibers and cells
32. 4-32
Cartilage
• Composed of chondrocytes located in
spaces called lacunae
• Next to bone firmest structure in body
• Types of cartilage
– Hyaline
– Fibrocartilage
– Elastic
33. 4-33
Hyaline Cartilage
• Found in areas for strong support and some flexibility
– Rib cage and cartilage in trachea and bronchi
• Forms most of skeleton before replaced by bone in embryo
• Involved in growth that increases bone length
36. 4-36
Bone
• Hard connective tissue that consists of
living cells and mineralized matrix
• Organic and inorganic
• Types
– Cancellous or spongy bone
– Compact bone
40. 4-40
Muscle Tissue
• Characteristics
– Contracts or shortens with force
– Moves entire body and pumps blood
• Types
– Skeletal
• Striated and voluntary
– Cardiac
• Striated and involuntary
– Smooth
• Nonstriated and involuntary
44. 4-44
Nervous Tissue
• Found in brain, spinal cord and nerves
• Ability to produce action potentials
• Cells
– Nerve cells or neurons
• Consist of dendrites, cell body, axons
• Consist of multipolar, bipolar, unipolar
– Neuroglia or support cells
