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VAN-504, Lecture - 02
Epithelia and their modifications.
Connective tissue and its components
including blood and bone
Tissues
• Definition: a group of closely associated cells
that perform related functions and are similar
in structure.
• Four basic types of tissue
function
– Epithelium
– Connective tissue
– Muscle tissue
– Nervous tissue
covering
support
movement
control
Epithelial Tissues
General Characteristics
1.Epithelial tissue is widespread throughout the body, covers
organs, and lines body surfaces.
2.Epithelial tissues - are anchored to a basement membrane
- are made up of tightly packed cells
- contain little intercellular material
- generally lack blood vessels, Avascular but innervated
- are replaced frequently, regeneration
3.Polarity
- Free upper (apical) surface
- Lower (basal) surface contributing basal lamina to basement membrane
Epithelia (plural)
• Epithelium: sheet of cells that covers a body surface
or lines a body cavity; also form most of the body’s
glands
• Functions:
Protection
Absorption
Sensory reception
Secretion
Filtration
Formation of slippery surfaces for movement
• Epithelial tissues function in protection,
secretion, absorption, excretion, and
sensory reception.
Epithelium
• Have one free (unattached)
surface or edge called the
apical surface
– Exposed to body’s
exterior or to the cavity
of an internal organ
• Lower surface of an
epithelium rests on a
basement membrane
– Structureless material
secreted by both the
epithelial cells and the
connective tissue cells
Classification of Epithelia
• According to thickness
– “simple” - one cell layer
– “stratified” – more than one layer of cells (which
are named according to the shape of the cells in
the apical layer)
• According to shape
– “squamous” – wider than tall
– “cuboidal” – as tall as wide
– “columnar” - taller than wide
Classification of Epithelium
• According to
relative number
of cell layers
– Simple (one
layer of cells)
– Stratified (more
than one cell
layer)
Classification of Epithelium
• According to the
shape of cells
– Squamous (cells
flattened like scales)
– Cuboidal (cubeshaped)
– Columnar (shaped
like columns)
Simple Squamous Epithelium
•Simple squamous (SS) tissue is composed of
flat, scale-like cells that usually forms
membranes.
•Single row of flat cells
•It lines the walls of blood vessels, pulmonary
alveoli (Shown in slide), and the lining of the
heart, lung, peritoneal cavities glomeruli,
endothelium, and serosa
• Permits diffusion of substances
• Secretes serous fluid
Simple Squamous Epithelium
Simple Cuboidal Epithelium
• This tissue is composed of a single layer of
cube-like cells with microvilli.
• Absorption and secretion, mucus production
• It lines the walls of kidney tubules, covers the
surface of ovaries, and is common in glands
and their ducts, Liver, thyroid, mammary and
salivary glands, bronchioles, and kidney tubules
Simple Cuboidal Epithelium
Simple Cuboidal Epithelium
Simple Columnar Epithelium
• This tissue is composed of a single layer of tall
narrow cells.
- oval nuclei in basal half of cell
• It often includes mucus-producing goblet cells.
• It often lines the digestive tract, uterus, kidney
and uterine tubes
• Absorption and secretion; mucus secretion.
Simple Columnar Epithelium
Simple Columnar Epithelium
Pseudo stratified Epithelium
• Secretes and propels respiratory mucus
• Although this tissue appears stratified, it is
actually composed of a single layer of cells of
different types. some not reaching free surface.
• Although their nuclei are found at different levels,
It give layer stratified look.
• Each cell adjoins the basal membrane (BM).
• This tissue lines the larger respiratory
passageways.
• It is often ciliated.
Pseudo stratified Epithelium
Pseudo stratified Columnar Epithelium
• Main functions: absorption and secretion
• Ciliated variety lines respiratory tract
– Mucus produced by goblet cells traps dust and other
debris
– Cilia propel mucus upward and away from the lungs
Stratified Epithelia
• More than one layer of cells
• Named for shape of surface cells
– exception is transitional epithelium
• Deepest cells on basement membrane
• Variations
– keratinized epithelium has surface layer of dead
cells
– Non keratinized epithelium lacks the layer of dead
cells
Stratified: regenerate from below
Keratinized Stratified Squamous
• Multilayered epithelium covered with dead squamous cells,
packed with keratin
– epidermal layer of skin
Nonkeratinized Stratified Squamous
• Multilayered surface epithelium forming
moist, slippery layer
• Tongue, oral mucosa, esophagus and vagina
Stratified Cuboidal Epithelium
•
•
Two or more cell layers; surface cells square
Secretes sweat; produces sperm and
hormones
• Sweat gland ducts; ovarian follicles and
seminiferous tubules
• Stratified cuboidal epithelium (SC) is found in
the ducts of sweat glands and surrounds
Graafian follicles of ovaries (shown below
Stratified Cuboidal Epithelium
Transitional Epithelium
• Multilayered epithelium surface cells that change from round to flat
when stretched
– allows for filling of urinary tract
– ureter and bladder
• Shape of cells depends upon the amount of stretching
• It lines organs of the urinary system.
Transitional Epithelium
Ciliated Epithelium
• Some epithelial membranes are made up of
cells with cilia, tiny projections that beat in
unison to move mucus along the surface.
• Ciliated epithelia in the trachea, for example,
sweep debris out of the respiratory tract.
Glandular Epithelium
• A gland is defined as one or more cells responsible for
secreting a particular product
• Two major gland types
– Endocrine gland
• Ductless since secretions diffuse into blood vessels
• All secretions are hormones
• Examples include pituitary, pancreas, ovaries, testes
– Exocrine gland
• Secretions empty through ducts to the epithelial
surface
• Include sweat and oil glands
Endocrine and Exocrine Glands
• Secrete substances
– composed of epithelial tissue
• Exocrine glands connect to surface with a duct
(epithelial tube)
• Endocrine glands secrete (hormones) directly into
bloodstream
• Mixed organs do both
– liver, gonads, pancreas
• Unicellular glands – endo or exocrine
– goblet or intrinsic cells of stomach wall
Connective Tissue
•
Connective tissue
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Connective tissue proper (examples: fat tissue, fibrous tissue of
ligaments)
Cartilage
Bone
Blood
• Widely spaced cells separated by fibers and ground substance
• Most abundant and variable tissue type
• Functions
–
–
–
–
connects organs
gives support and protection (physical and immune)
stores energy and produces heat
movement and transport of materials
Cells of Connective Tissue
• Fibroblasts produce fibers and ground substance
• Macrophages phagocytize foreign material and
activate immune system
– arise from monocytes (WBCs)
• Neutrophils wander in search of bacteria
• Plasma cells synthesize antibodies
– arise from WBCs
• Mast cells secrete
– heparin inhibits clotting
– histamine that dilates blood vessels
• Adipocytes store triglycerides
Fibers of Connective Tissue
• Collagen fibers (white fibers)
– tough, stretch resistant, yet flexible
– tendons, ligaments and deep layer of the skin
• Reticular fibers
– thin, collagen fibers coated with glycoprotein
– framework in spleen and lymph nodes
• Elastic fibers (yellow fibers)
– thin branching fibers of elastin protein
– stretch and recoil like rubberband (elasticity)
– skin, lungs and arteries stretch and recoil
Connective Tissue Ground Substance
• Gelatinous material between cells
– absorbs compressive forces
• Consists of 3 classes of large molecules
– glycosaminoglycans – chondroitin sulfate
• disaccharides that attract sodium and hold water
• role in regulating water and electrolyte balance
– Proteoglycan (bottlebrush-shaped molecule)
• create bonds with cells or extracellular macromolecules
– adhesive glycoproteins
• protein-carbohydrate complexes bind cell membrane to
collagen outside the cells
Classes of Connective Tissue
Fibrous Connective Tissue Types
• Loose connective tissue
– gel-like ground substance between cells
– types
• areolar
• reticular
• adipose
• Dense connective tissue
– fibers fill spaces between cells
– types vary in fiber orientation
• dense regular connective tissue
• dense irregular connective tissue
Areolar Tissue
• Loose arrangement of fibers and cells in
abundant ground substance
• Underlies all epithelia, between muscles,
passageways for nerves and blood vessels
Areolar Tissue
Reticular Tissue
• Loose network of reticular fibers and cells
• Forms supportive stroma (framework) for lymphatic organs
• Found in lymph nodes, spleen, thymus and bone marrow
Reticular Tissue
Adipose Tissue
• Empty-looking cells with thin margins; nucleus pressed against cell
membrane
• Energy storage, insulation, cushioning
– subcutaneous fat and organ packing
– brown fat (hibernating animals) produces heat
Adipose Tissue
Dense Regular Connective Tissue
• Densely, packed, parallel collagen fibers
– compressed fibroblast nuclei
• Tendons and ligaments hold bones together and attach muscles to
bones
Dense regular Connective Tissue
Dense Irregular Connective Tissue
• Densely packed, randomly arranged, collagen fibers and
few visible cells
– withstands stresses applied in different directions
– deeper layer of skin; capsules around organs
Dense Irregular Connective Tissue
Cartilage
• Supportive connective tissue with rubbery
matrix
• Chondroblasts produce matrix
– called chondrocytes once surrounded
• No blood vessels
– diffusion brings nutrients and removes wastes
– heals slowly
• Types of cartilage vary with fiber types
– hyaline, fibrocartilage and elastic cartilage
Hyaline Cartilage
• Rubbery matrix; dispersed collagen fibers; clustered chondrocytes
in lacunae
– supports airway, eases joint movements
• Ends of bones at movable joints; sternal ends of ribs; supportive
material in larynx, trachea, bronchi and fetal skeleton
Hyaline Cartilage
Elastic Cartilage
• Hyaline cartilage with elastic fibers
• Provides flexible, elastic support
– external ear and epiglottis
Elastic Cartilage
Fibrocartilage
• Hyaline cartilage with extensive collagen fibers (never has
perichondrium)
• Resists compression and absorbs shock
– pubic symphysis, meniscus and intervertebral discs
Fibrocartilage
Bone
• Spongy bone - spongy in appearance
– delicate struts of bone
– covered by compact bone
– found in heads of long bones
• Compact bone - solid in appearance
– more complex arrangement
– cells and matrix surround vertically oriented blood
vessels in long bones
Bone Tissue (compact bone)
• Calcified matrix in lamellae around central canal
• Osteocytes in lacunae between lamellae
• Skeletal support; leverage for muscles; mineral
storage
Bone
Blood
• Variety of cells and cell fragments; some with
nuclei and some without
• Nonnucleated pale pink cells or nucleated
white blood cells
• Found in heart and blood vessels
Blood
Mast Cell
Lymphocytes
Microphages
Nervous Tissue
–Nervous tissue
• Neurons
• Supporting cells
• Large cells with long cell processes
– surrounded by smaller glial cells lacking processes
• Internal communication between cells
– in brain, spinal cord, nerves and ganglia
Nervous Tissue
Muscle Tissue
• Elongated cells stimulated to contract
• Exert physical force on other tissues
– move limbs
– push blood through a vessel
– expel urine
• Source of body heat
• 3 histological types of muscle
– skeletal,
– cardiac and
– smooth
Skeletal Muscle
• Long, cylindrical, unbranched cells with striations and
multiple peripheral nuclei
– movement, facial expression, posture, breathing, speech,
swallowing and excretion
Skeletal Muscle
Cardiac Muscle
• Short branched cells with striations and intercalated
discs
– one central nuclei per cell
• Pumping of blood by cardiac (heart) muscle
Cardiac Muscle
Smooth Muscle
• Short fusiform cells; nonstriated with only one central nucleus
– sheets of muscle in viscera; iris; hair follicles and sphincters
– swallowing, GI tract functions, labor contractions, control
of airflow, erection of hairs and control of pupil
Smooth Muscle