Chapter 4
Histology: Study of Tissues
TISSUE TYPES
•
•
•
•
Epithelial
Connective
Muscle
Nervous
Embryonic Development
• Blastocyst- ball of cells
• Germ layers:
– Endoderm- outer layer
– Mesoderm- middle layer
– Ectoderm- inner layer
Gastrulation- process of blastocyst to germ
layers
Histogenesis- process of germ layers
developing into different kinds of tissues.
Epithelial Tissue
• Types & locations
– membranous: cover/lining; found in serous
cavities, bld & lymph vessels, respiratory,
digestive & genitourinary tracts.
– Glandular: grouped in solid cords or
specialized follicles that form secretory
units of endocrine & exocrine glands.
Epithelial Tissue
• Functions
–
–
–
–
–
Protection
Sensory functions
Secretion
Absorption
Excretion
Epithelial Tissue
• Generalizations
–
–
–
–
–
Limited matrix material
Connects to connective tissue
Avascular
Cells tightly packed
Frequently replace themselves
Epithelial Tissue
• Classifications
– Membranous epithelium
• Classification based on cells shape
– Squamous cells
– Cubiodal cells
– Columnar cells
– Pseudostratified columnar cells
Epithelial Tissue
• Classifications
– Classification based on layers of cells
• Simple epithelium
• Stratified epithelium
• Transitional epithelium
Epithelial Tissue
• Glandular epithelium
– Unicellular glands- single-celled glands;
Goblet Cells
– Multicellular glands- clusters, solid cords,
specialized follicles
– Exocrine glands- secrete into ducts
– Endocrine glands- ductless glands
Connective Tissue Categories
• Embryonic or mesenchyme
• Adult
–
–
–
–
–
–
Loose
Dense
Connective tissue with special properties
Cartilage
Bone
Blood
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
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
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
Connective Tissue with Special
Properties
• Adipose tissue- Fat storage
– 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
Cartilage
• Composed of chondrocytes
located in spaces called
lacunae
• Next to bone firmest
structure in body
• Types of cartilage
– Hyaline
– Fibrocartilage
– Elastic
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
Fibrocartilage
• Slightly compressible and very tough
• Found in areas of body where a great deal of
pressure is applied to joints
– Knee, jaw, between vertebrae
Elastic Cartilage
• Rigid but elastic properties
– External ears, epiglottis
Osseous Tissue
• Commonly called
bone tissue
• Function is to
support & protect
• Made of osteocytes
• Compact Bone
• Cancellous or Spongy
Bone
Blood
• Matrix between
the cells is liquid
• Hemopoietic
tissue
– Forms blood cells
– Found in bone
marrow
• Yellow
• Red
Muscle Tissue
• Characteristics
– Contracts or shortens with force
– Moves entire body and pumps blood
• Types
– Skeletal- moves bones
• Striated and voluntary
– Cardiac- pumps heart
• Striated and involuntary
– Smooth- covers organs; moves fluids
• Nonstriated and involuntary
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
Membranes
• Mucous
– Line cavities that open to
the outside of body
– Secrete mucus
• Serous
– Line cavities not open to
exterior
• Pericardial, pleural,
peritoneal
• Synovial
– Line freely movable joints
– Produce fluid rich in
hyaluronic acid
Inflammation
• Response when tissues
damaged or with an
immune response
• Manifestations
– Redness, heat,
swelling, pain,
disturbance of
function
• Mediators
– Include histamine,
kinins, prostaglandins,
leukotrienes
– Stimulate pain
receptor and increase
blood vessel
permeability