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