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Histology
Human Anatomy and Physiology
What Is a Tissue? Tissue = cells organized
into layer or groups Cells separated by
nonliving, intercellular materials Solid minerals in bone Liquid plasma in blood
How Are Tissues Maintained? Stem cells = cells
that have the ability to divide many times and yield new cells that then specialize
Groups of stem cells set aside in tissues to replace worn or damaged parts
4 Major Types of Tissues
S im p le S q u am ou s S im p le C u b o id a l
S im p le C o lu m n ar P seu d os tra tified C o lu m n ar
S tra tified S q u am ou s S tra tified C u b o id a l
S tra tified C o lu m n ar Tran s it ion a l
E xoc rin e G lan d s E n d oc rin e G lan d s
G lan d u la r
E p ith e lia l
A reo la r (L oose) A d ip ose
R eticu la r D en se
E las tic
H ya lin e E las tic
F ib rocartilag e
C artilag e
B on e B lood
C on n ec tive
S ke le ta l S m ooth
C ard iac
M u sc le N ervou s
Tissu es
Embryonic Germ Layers
General Characteristics of Epithelial Tissue
Widespread throughout the body
Basement membrane Lacks blood vessels Divides readily Tightly packed Classified according to
shape and number of layers
Simple Squamous Epithelium
Simple Squamous continued…
Functions: Allows substances to
pass easily Forms walls of capillaries Lines air sacs (alveoli) of
lungs Lines insides of blood
and lymph vessels Covers membranes that
line body cavities
Simple Cuboidal Epithelium
Simple Cuboidal continued… Functions:
Covers the ovaries Lines the kidney
tubules Lines ducts of the
salivary glands, pancreas, and liver
Secretion and absorption
Simple Columnar Epithelium May be ciliated or
nonciliated Goblet cells Microvilli Functions:
Absorption Movement of
substances Secretion
Nonciliated Simple Columnar Epithelium
Ciliated Simple Columnar Epithelium
Pseudostratified Columnar Epithelium
Pseudostratified Columnar continued…
Functions: Lines the passages
of the respiratory system
Lines ducts of glands and sperm-carrying ducts
Stratified Squamous Epithelium
Stratified Squamous continued… Functions:
Keratinized form makes up the epidermis
Nonkeratinized lines the oral cavity, throat, vagina, and anal canal
Stratified Cuboidal Epithelium Functions:
Lines larger ducts of mammary glands, sweat glands, salivary glands, and pancreas
Forms lining of developing ovarian follicles and seminiferous tubules
Stratified Columnar Epithelium Functions:
Lines vas deferens and some parts of the pharynx
Protection Secretion
Transitional Epithelium
Transitional Epithelium continued… Functions:
Forms the inner lining of the urinary bladder
Lines the ureters and part of the urethra
Expandable lining Blocks urine from
diffusing back into the body
Glandular Epithelium Specialized to produce and secrete
substances into ducts or into body fluids Glands classified as endocrine or exocrine
E n d oc rin esec re tes p rod u c ts in to t is su e
flu id s o r b lood
M eroc rin ere lease flu id p rod u c ts
b y exocytos is
A p oc rin elose sm a ll p o rt ion s o f
g lan d u la r ce lls
H o loc rin ere lease en tire ce lls
th a t la te r d is in teg ra te
E xoc rin esec re tes p rod u c ts in to d u c ts th a t
op en on to an in te rn a l o rexte rn a l su rface
Typ es o f G lan d s
Endocrine Glands Pituitary gland, thyroid gland, parathyroid
glands, adrenal glands, pancreas Will be discussed in more detail later
Exocrine Glands Goblet cells Intestinal glands, sweat glands, mucous
glands in small intestine, sebaceous glands, bulbourethral glands of male, salivary glands
Classification of Connective Tissue
Mesenchyme
General Characteristics of Connective Tissue Most abundant type
of tissue by weight Large amounts of
matrix between cells Matrix contains
fibers and ground substance
Vascularity
Major cell types: Fibroblast Macrophage Mast Cell
Fiber types: Collagenous Elastic Reticular
Connective tissue proper and specialized connective tissues
Areolar Connective Tissue Also known as loose connective tissue Mainly fibroblasts Collagenous and elastic fibers
Areolar Connective Tissue continued…
More Areolar Connective Tissue
Functions: Binds the skin to
underlying organs Fills spaces between
muscles Lies beneath most
epithelium layers Blood vessels
nourish epithelial cells
Adipose Tissue Also known as fat Adipocytes store fat in their cytoplasm Amount in the body reflects diet or endocrine
disorder
Adipose Tissue continued… Functions:
Lies beneath skin, in spaces between muscles, around the kidneys, behind the eyeballs, in some abdominal membranes, on the surface of the heart, in breasts, and around some joints
Cushions joints and some organs
Insulation Stores energy
Reticular Connective Tissue Reticular fibers Numerous fibroblasts and white blood cells
Reticular Tissue continued… Function:
Provides supportive framework in walls of certain internal organs, such as the liver, spleen, and lymphatic organs
Regular Dense Connective Tissue
Closely packed collagenous fibers, fine network of elastic fibers
Few cells, mostly fibroblasts Regular dense connective tissue – very organized
fibers
Regular Dense continued… Functions:
Attaches muscles to bones or to other muscles
Attaches bones to bones
Withstands great tensile stress when pulling force is applied in one direction
Makes up tendons and most ligaments
Irregular Dense Connective Tissue
Thicker, interwoven, and more randomly organized fibers
Irregular Dense continued… Functions:
Able to withstand tension exerted in many directions
Provides structural strength
Makes up dermis of skin, submucosa of digestive tract, fibrous capsules
Elastic Connective Tissue Elastic fibers in parallel strands or branching networks Collagenous fibers and fibroblasts between elastic fibers Found in ligamenta flava and within walls of some large
arteries, some portions of the heart, and larger airways
Cartilage Rigid connective tissue Functions:
Provides support, frameworks, and attachments Protects underlying tissues Forms structural models for developing bones
Many collagenous fibers Chondrocytes and lacunae Perichondrium Lacks direct blood supply Types distinguished by types of intercellular material
Hyaline Cartilage Most common type of cartilage Collagenous fibers form imperceptible network Chondroblasts form matrix and mature into
chondrocytes
Hyaline Cartilage continued… Functions:
Supports and reinforces Has resilient cushioning
properties Resists compression
stress Found on ends of bones
in joints, soft part of nose, trachea, larynx, and costal cartilages of ribs
Forms most of embryonic skeleton
Important in bone growth and repair of fractures
Elastic Cartilage More flexible than hyaline cartilage Elastic fibers in matrix
Elastic Cartilage continued… Functions:
Maintains the shape of a structure while allowing greater flexibility
Provides the framework for the external ears and parts of the larynx
Fibrocartilage Very tough cartilage Many large collagenous fibers
Fibrocartilage continued… Functions:
Tensile strength Shock absorber Forms intervertebral
disks, disks in knee joint, and pubic symphysis
Compact Bone Also called osseous tissue Most rigid connective tissue Mineral salts in matrix Large amounts of collagen Osteocytes
Bone continued… Functions:
Supports and protects by enclosing
Provides levers for muscles to act on
Stores calcium and other minerals
Marrow inside bones is site of hematopoiesis
Blood Blood plasma Red blood cells, white blood cells, and platelets Most blood cells formed in red bone marrow Functions: transport gases, fight infection, clotting Will be discussed in more detail later
General Characteristics of Muscle Tissues Contractile Elongated cells Three types
classified according to striations and nuclei
Will be discussed more later
S ke le ta l S m ooth C ard iac
Typ es o f M u sc le
Skeletal Muscle Long and narrow cells Striations Multinucleate cells
Skeletal Muscle continued… Functions:
Voluntary movement Locomotion Manipulation of the
environment Facial expression Voluntary control Attached to bones
and occasionally skin
Smooth Muscle No striations Spindle-shaped cells Single, centrally located nucleus
Smooth Muscle continued… Functions:
Propels substances or objects along internal passageways
Involuntary Found mostly in
walls of hollow organs
Cardiac Muscle Striated cells joined end to end Cells form complex, branching network Intercalated disks Usually uninucleate
Cardiac Muscle continued… Functions:
Involuntary Propels blood into
the circulation Found only in the
heart
General Characteristics of Nervous Tissue Neurons Neuroglia Will be discussed more later
Nervous Tissue continued… Functions:
Transmits electrical signals from sensory receptors and to effectors (muscles and glands)
Found in brain, spinal cord, and nerves