Chapter 4
Intro to Histology
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Interpreting Tissue
Sections
-------------------------
Tissue Types
--------------------------
Intracelluar Junctions
Histology
•
Histology (microscopic anatomy)
– the study of tissues and how they are arranged into
organs
•
Structural Hierarchy of the Human Body
– Cells / tissues / organs / systems
•
Tissue
– a group of similar cells and cell products
– arise from the same region of the embryo
– work together to perform a specific structural or
physiological role in an organ.
•
Organ
– structure with discrete boundaries
– composed of two or more tissue types // usually all four
tissue type will be required to form an organ
Modern Cell Theory
•
All organisms composed of cells and cell
products.
•
Cell is the simplest structural and functional
unit of life.
– cells are alive
•
An organism’s structure and functions are due
to the activities of its cells.
•
Cells come only from preexisting cells, not from
nonliving matter.
– therefore, all life traces its ancestry to the same
original cells
•
Cells of all species have many fundamental
similarities in their chemical composition and
metabolic mechanisms.
The Study of Tissues
• 50 trillion cells of 200 different cell
types in human body – however!
• four broad categories of tissues
– epithelial tissue
– connective tissue
– nervous tissue
– muscular tissue
Primary Tissue Classes
• four primary tissues differ from one another in the:
– types and functions of their cells
– the characteristics of the matrix (extracellular material)
– the relative amount of space occupied by cells versus the
matrix
• the matrix (extracellular material) is composed of :
– “hydrated” fibrous proteins = clear gel substance
– Often referred to as:
•
•
•
•
•
ground substance
tissue fluid
extracellular fluid (ECF)
interstitial fluid
tissue gel
Overview of Tissue
• Epithelial (simple / stratified / shape of cell)
• Muscle (skeletal / smooth / cardiac)
• Connective tissue
– Connective tissue proper (general categories)
• Dense / Irregular (describes arrangement of fibers)
– Connective tissue types
•
•
•
•
•
•
Fibrous loose (areolar / reticular)
Fibrous dense (regular / irregular)
Adipose
Bone
Blood
Cartilage (hyaline / elastic / fibrous)
• Nervous
– voluntary or involuntary nervous system
– Central or peripheral nervous system
Nervous tissue: Internal communication
• Brain
• Spinal cord
• Nerves
Muscle tissue: Contracts to cause movement
• Muscles attached to bones (skeletal)
• Muscles of heart (cardiac)
• Muscles of walls of hollow organs (smooth)
Epithelial tissue: Forms boundaries between different
environments, protects, secretes, absorbs, filters
• Lining of digestive tract organs and other hollow
organs
• Skin surface (epidermis)
Connective tissue: Supports, protects, binds
other tissues together
• Bones
• Tendons
• Fat and other soft padding tissue
Interpreting Tissue
Sections
Interpreting Tissue Sections
• preparation of histological specimens
– fixative prevents decay (formalin)
– histological sections – tissue is sliced
into thin sections one or two cells thick
– stains – tissue is mounted on slides and
artificially colored with histological stain
• stains bind to different cellular components
• Sectioning reduces three-dimensional
structure into a two-dimensional slice
Sectioning Solid Objects
• sectioning a cell
with a centrally
located nucleus
• some slices
miss the cell
nucleus
• in some the
nucleus is
smaller
Sectioning Hollow Structures
• cross section of
blood vessel, gut,
or other tubular
organ.
• longitudinal
section of a
sweat gland.
notice what a
single slice could
look like.
(c)
Types of Tissue Sections
Longitudinal sections
• longitudinal section (l.s.)
– tissue cut along long
direction of organ
Cross sections
• cross section (c.s. or
x.s.) or transverse
section (t.s.)
– tissue cut perpendicular to
length of organ
Oblique sections
• oblique section
– tissue cut at angle between
cross and longitudinal
section
Non-sectioned Preparation
• Smear – tissue is rubbed or
spread across the slide
– spinal cord or blood
• Spread – cobwebby tissue is
laid out on a slide
– areolar tissue
Tissue Types
Epithelial Tissue Functions
•
•
•
•
•
•
Protection
Absorption
Filtration
Excretion
Secretion
Sensory reception
Epithelial Tissue
•
consists of a flat sheet of closely adhering cells
•
one or more cells thick
•
“free surface” / upper surface usually exposed to the environment or an
internal space in the body
•
Basal surface always lie on a layer of loose connective / which provides
the blood vessels for nourishment and waste removal
•
covers body surface or lines body cavities
•
forms the external and internal linings of many organs
•
constitutes most glands
•
extracellular material is so thin it is not visible with a light microscope
•
avascular (no blood vessels)
•
Contains nerves
•
tissue allows no room for blood vessels
Polar Epithelium and the Basement Membrane
•
Epithelial tissue is “polar”
– basal surface – surface of an epithelial cell that faces the
basement membrane
– apical surface – surface of an epithelial cell that faces the
“free surface”
– away from the basement membrane (microvilli / cilia)
•
Basement membrane
– layer between the epithelial cells and the underlying
connective tissue
– In skin it is between the epithelial cells and dermis
– anchors the epithelium to the connective tissue below it
– Non-cellular substance secreted by epithelial cells
– basement membrane contains:
• collagen
• laminin and fibronectin adhesive glycoproteins
• heparin sulfate - large protein-carbohydrate complex
The Basement Membrane
•
Basement membrane has two layers
– basal lamina (superficial)
– reticular lamina (deep)
•
Basal lamina
–
–
–
–
–
–
–
–
•
Non-cellular glycoproteins
Secreted by epithelial cells
Reinforces epithelial sheet
Resists stretching and tearing
Acts as a selective filter
Defines epithelial boundary
Few but some very fine collagen fibers
Scaffolding for cell migration in wound repair
Reticular lamina
– Deep to basal lamina
– Network of collagen fibers
– Belongs to underlying connective tissue
Epithelial Cells Shapes and Classes
• Simple epithelium
– contains one layer of cells
– named by shape of cells
– all cells touch the basement membrane
• Stratified epithelium
–
–
–
–
contains more than one layer
named by shape of apical cells
cells rest on top of others
some cells do not touch basement
membrane
Simple Epithelia
• four types of simple epithelia
• three named for their cell shapes
– simple squamous (thin scaly cells)
– simple cuboidal (square or round cells)
– simple columnar (tall narrow cells)
• fourth type
– pseudostratified columnar
•
•
•
•
not all cells reach the free surface
shorter cells are covered over by taller ones
looks stratified
every cell reaches the basement membrane
Simple Epithelia Unicellular Glands
• goblet cells
– Wine glass shaped mucus secreting
cells in simple columnar and
pseudostratified epithelia
– These are exocrine glands
– Other unicellular secretory cells exist
that do not look like a wine glass
Goblet cell (unicellular exocrine gland).
Microvilli
Secretory
vesicles
containing
mucin
Golgi
apparatus
Rough ER
Nucleus
Simple Squamous Epithelium
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Squamous epithelial cells
Nuclei of smooth muscle
Basement membrane
(b)
(a)
•
•
•
•
single row of thin cells
permits rapid diffusion or transport of substances
secretes serous fluid
alveoli, glomeruli, endothelium, and serosa (Note:
insert shows serosa of small intestine)
Simple squamous epithelium
Description: Single layer of
flattened cells with disc-shaped
central nuclei and sparse
cytoplasm; the simplest of the
epithelia.
Air sacs
of lung
tissue
Nuclei of
squamous
epithelial
cells
Function: Allows materials to pass
by diffusion and filtration in sites
where protection is not important;
secretes lubricating substances in
serosae.
Location: Kidney glomeruli; air
sacs of lungs; lining of heart, blood
vessels, and lymphatic vessels;
lining of ventral body cavity
(serosae).
Photomicrograph: Simple squamous
epithelium forming part of the alveolar
(air sac) walls (140x).
Simple Cuboidal Epithelium
Lumen of kidney tubule
(a)
Cuboidal epithelial cells
Basement membrane
(b)
• single layer of square or round cells
• absorption and secretion, mucus production and
movement
• liver, thyroid, mammary and salivary glands, bronchioles,
and kidney tubules
Simple cuboidal epithelium
Description: Single layer of
cubelike cells with large, spherical
central nuclei.
Simple
cuboidal
epithelial
cells
Nucleus
Function: Secretion and
absorption.
Basement
membrane
Location: Kidney tubules; ducts
and secretory portions of small
glands; ovary surface.
Connective
tissue
Photomicrograph: Simple cuboidal
epithelium in kidney tubules (430x).
Simple Columnar Epithelium
Brush border
(microvilli)
(a)
Connective
tissue
Basement
membrane
Goblet
Nuclei cell
Columnar
cells
(b)
•
single row tall, narrow cells
– oval nuclei in basal half of cell
– brush border of microvilli, ciliated in some organs, may
possess goblet cells
•
•
absorption and secretion; mucus secretion
lining of GI tract, uterus, kidney and uterine tubes
Simple columnar epithelium
Description: Single layer of tall
cells with round to oval nuclei;
some cells bear cilia; layer may
contain mucus-secreting
unicellular glands (goblet cells).
Microvilli
Simple
columnar
epithelial
cell
Function: Absorption; secretion
of mucus, enzymes, and other
substances; ciliated type propels
mucus (or reproductive cells) by
ciliary action.
Location: Nonciliated type lines
most of the digestive tract
(stomach to rectum), gallbladder,
and excretory ducts of some
glands; ciliated variety lines small
bronchi, uterine tubes, and some
regions of the uterus.
Mucus of
goblet cell
Basement
membrane
Photomicrograph: Simple columnar
epithelium of the small intestine mucosa (660x).
Pseudostratified Epithelium
(not covered in lab exercise)
Cilia
(a)
Basement membrane
(b)
•
looks multilayered; some not reaching free
surface; all touch basement membrane
– nuclei at several layers
– with cilia and goblet cells
•
•
secretes and propels mucus
respiratory tract and portions of male urethra
Basal cells Goblet cell
Pseudostratified columnar epithelium
Description: Single layer of cells
of differing heights, some not
reaching the free surface; nuclei
seen at different levels; may
contain mucus-secreting cells
and bear cilia.
Cilia
Pseudostratified
epithelial
layer
Function: Secrete substances,
particularly mucus; propulsion of
mucus by ciliary action.
Location: Nonciliated type in
male’s sperm-carrying ducts and
ducts of large glands; ciliated
variety lines the trachea, most of
the upper respiratory tract.
Trachea
Photomicrograph: Pseudostratified
ciliated columnar epithelium lining the
human trachea (800x).
Basement
membrane
Stratified Epithelia
•
•
•
•
range from 2 to 20 or more layers of cells
some cells resting directly on others
only the deepest layer attaches to the basement membrane
three stratified epithelia are named for the shapes of their
surface cells
– stratified squamous
– stratified cuboidal
– stratified columnar (rare)
•
fourth type
– transitional epithelium
•
•
most widespread epithelium in the body
deepest layers undergo continuous mitosis
– their daughter cells push toward the surface and become flatter
as they migrate farther upward
– finally die and flake off – exfoliation or desquamation
•
two kinds of stratified squamous epithelia
– keratinized – found on skin surface, abrasion resistant
– nonkeratinized – lacks surface layer of dead cells
Keratinized Stratified Squamous
Dead squamous cells
Living epithelial cells
Dense irregular
connective tissue
Areolar tissue
(a)
•
•
•
•
(b)
multiple cell layers with cells becoming flat and scaly toward surface
epidermis; palms and soles heavily keratinized
resists abrasion; retards water loss through skin; resists penetration
by pathogenic organisms
Cutaneous membrane
Nonkeratinized Stratified Squamous
Living epithelial cells
(a)
•
•
•
•
Connective tissue
(b)
same as keratinized epithelium without the surface layer of dead cells
tongue, oral mucosa, esophagus and vagina
resists abrasion and penetration of pathogens
Adult vagina, oral cavity, esophagus
Stratified Cuboidal Epithelium
(not covered in lab exercise)
Cuboidal cells
(a)
Epithelium
Connective tissue
(b)
• two or more cell layers; surface cells square or round
• secretes sweat; sperm production and produces ovarian
hormones
• sweat gland ducts; ovarian follicles and seminiferous
tubules
Transitional Epithelium
Basement
membrane
(a)
Connective
tissue
Binucleate
epithelial cell
(b)
• multilayered epithelium surface cells that change
from round to flat when stretched
• allows for filling of urinary tract
• ureter and bladder
Transitional epithelium
Description: Resembles both
stratified squamous and stratified
cuboidal; basal cells cuboidal or
columnar; surface cells dome
shaped or squamouslike,
depending on degree of organ
stretch.
Transitional
epithelium
Function: Stretches readily,
permits stored urine to distend
urinary organ.
Location: Lines the ureters,
bladder, and part of the urethra.
Photomicrograph: Transitional epithelium
lining the bladder, relaxed state (360x); note
the bulbous, or rounded, appearance of the
cells at the surface; these cells flatten and
elongate when the bladder fills with urine.
Basement
membrane
Connective
tissue
Connective Tissue
• a type of tissue in which cells usually occupy less
space than the extracellular material
• binds organs to each other
• support and protect organs
• most cells of connective tissue are not in direct
contact with each other
– separated by extracellular material (matrix / ground
substance)
• highly vascular – richly supplied with blood
vessels
• most abundant, widely distributed, and
histologically variable of the primary tissues
Functions of Connective Tissue
• binding of organs – tendons and ligaments
• support – bones and cartilage
• physical protection – cranium, ribs,
sternum
• immune protection – white blood cells
attack foreign invaders
• movement – bones provide lever system
• storage – fat, calcium, phosphorus
• heat production – metabolism of brown fat
in infants
• transport - blood
Components of Fibrous Connective Tissue
(Cells / Fibers / Matrix)
• Cells
– fibroblasts produce fibers and ground
substance
– adipocytes store triglycerides (fat molecules)
– Blood’s formed elements
• macrophages phagocytize foreign material and
activate immune system when sense foreign
matter (antigen)
– arise from white blood cell - monocytes
• leukocytes or white blood cells
– neutrophils wander in search of and attacking
bacteria
– lymphocytes react against bacteria, toxins, and
other foreign material
• plasma cells synthesize disease fighting
antibodies
– arise from lymphocytes
• mast cells – found along side of blood vessels
– secrete heparin inhibits clotting
– histamine that dilates blood vessels
Components of Fibrous Connective Tissue
(Cells / Fibers / Matrix)
•
Fibers
– collagenous fibers
• most abundant of the body’s proteins – 25%
• tough, flexible, and resist stretching
• tendons, ligaments, and deep layer of the skin are
mostly collagen
• less visible in matrix of cartilage and bone
• White fibers
– reticular fibers
• thin collagen fibers coated with glycoprotein
• form framework of such organs as spleen and
lymph nodes
– elastic fibers
•
•
•
•
•
thinner than collagenous fibers
branch and rejoin each other
made of protein called elastin
allows stretch and recoil
yellow fibers – fresh elastic fibers
Components of Fibrous Connective Tissue
(Cells / Fibers / Matrix)
•
Ground Substance / Matrix
– usually a gelatinous to rubbery consistency resulting
from three classes of large molecules
– glycosaminoglycans (GAG)
• long polysaccharide composed of unusual
disaccharides called amino sugars and uronic acid
• play important role of regulating water and electrolyte
balance in the tissues
• chondroitin sulfate – most abundant GAG
– in blood vessels and bone
– responsible for stiffness of cartilage
• hyaluronic acid – viscous, slippery substance that
forms an effective lubricant in joints and constitutes
much of the vitreous body of the eyeball
– proteoglycan
• gigantic molecule shaped like a test-tube brush
• forms thick colloids that creates strong structural bond
between cells and extracellular macromolecules –
holds tissues together
– adhesive glycoproteins – bind components of tissues
together
Cell types
Macrophage
Fibroblast
Lymphocyte
Fat cell
Mast cell
Neutrophil
Capillary
Extracellular
matrix
Ground substance
Fibers
• Collagen fiber
• Elastic fiber
• Reticular fiber
Fibrous Connective Tissue
• loose connective tissue
– much gel-like ground
substance between cells
– types
• areolar
• reticular
• dense connective tissue
– fibers fill spaces between cells
– types vary in fiber orientation
• dense regular connective tissue
• dense irregular connective tissue
Tendons
Fibrous Loose Connective Tissue
(Also Known as Areolar Tissue)
•
loosely organized fibers, abundant blood vessels, and a
lot of seemingly empty space
•
possess all six cell types
•
fibers run in random directions
– mostly collagenous, but elastic and reticular also present
•
found in tissue sections from almost every part of the
body
– surrounds blood vessels and nerves
•
nearly every epithelium rests on a layer of areolar tissue
– blood vessels provide nutrition to epithelium and waste
removal
– ready supply of infection fighting leukocytes that move
about freely in areolar tissue
Fibrous Loose CT / Areolar Tissue
Ground
substance
(a)
Elastic
fibers
Collagenous
fibers
Fibroblasts
(b)
• loosely organized fibers, abundant blood vessels, and a
lot of seemingly empty space
• underlies all epithelia, in serous membranes, between
muscles, passageways for nerves and blood vessels
Fibrous Loose CT / Areolar Tissue
Connective tissue proper: loose connective tissue, areolar
Description: Gel-like matrix with
all three fiber types; cells:
fibroblasts, macrophages, mast
cells, and some white blood cells.
Function: Wraps and cushions
organs; its macrophages
phagocytize bacteria; plays
important role in inflammation;
holds and conveys tissue fluid.
Location: Widely distributed
under epithelia of body, e.g., forms
lamina propria of mucous
membranes; packages organs;
surrounds capillaries.
Elastic
fibers
Ground
substance
Fibroblast
nuclei
Collagen
fibers
Epithelium
Lamina
propria
Photomicrograph: Areolar connective
tissue, a soft packaging tissue of the body (340x).
Fibrous Loose CT / Reticular Tissue
Leukocytes
(a)
Reticular
fibers
(b)
• mesh of reticular fibers and fibroblasts
• forms supportive stroma (framework) for
lymphatic organs
• found in lymph nodes, spleen, thymus and bone
marrow
Fibrous Loose CT / Reticular Tissue
Connective tissue proper: loose connective tissue, reticular
Description: Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on
the network.
Function: Fibers form a soft
internal skeleton (stroma) that
supports other cell types including
white blood cells, mast cells, and
macrophages.
White blood
cell
(lymphocyte)
Location: Lymphoid organs
(lymph nodes, bone marrow, and
spleen).
Spleen
Reticular
fibers
Photomicrograph: Dark-staining network
of reticular connective tissue fibers forming
the internal skeleton of the spleen (350x).
Fibrous Dense Regular Connective Tissue
Collagen fibers
(a)
Ground substance
Fibroblast nuclei
(b)
• densely, packed, parallel collagen fibers
– compressed fibroblast nuclei
• tendons attach muscles to bones and ligaments
hold bones together
Fibrous Dense Regular Connective Tissue
Connective tissue proper: dense connective tissue, dense regular
Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.
Function: Attaches muscles to
bones or to muscles; attaches
bones to bones; withstands great
tensile stress when pulling force is
applied in one direction.
Collagen
fibers
Location: Tendons, most
ligaments, aponeuroses.
Nuclei of
fibroblasts
Shoulder
joint
Ligament
Tendon
Photomicrograph: Dense regular connective
tissue from a tendon (430x).
Fibrous Dense Irregular Connective Tissue
Bundles of
Gland
collagen fibers ducts
(a)
Fibroblast Ground
nuclei
substance
(b)
• densely packed, randomly arranged, collagen
fibers and few visible cells
– withstands unpredictable stresses
– deeper layer of skin; capsules around organs
Connective tissue proper: dense connective tissue, dense irregular
Description: Primarily irregularly
arranged collagen fibers; some
elastic fibers; fibroblast is the
major cell type.
Nuclei of
fibroblasts
Function: Withstands tension
exerted in many directions;
provides structural strength.
Location: Fibrous capsules of
organs and of joints; dermis of the
skin; submucosa of digestive tract.
Collagen
fibers
Shoulder
joint
Fibrous
joint
capsule
Photomicrograph: Dense irregular connective
tissue from the fibrous capsule of a joint (430x).
Connective tissue proper: dense connective tissue, elastic
Description: Dense regular
connective tissue containing a
high proportion of elastic fibers.
Function: Allows tissue to recoil
after stretching; maintains pulsatile
flow of blood through arteries; aids
passive recoil of lungs following
inspiration.
Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within
the walls of the bronchial tubes.
Elastic
fibers
Aorta
Heart
Photomicrograph: Elastic connective tissue
in the wall of the aorta (250x).
Bone
• ‘bone’ has two meanings:
– an organ of the body; femur, mandible; composed of multiple
tissue types
– bone tissue – osseous tissue – makes up most of the mass of
bone
• two forms of osseous tissue
– spongy bone - spongy in appearance
• delicate struts of bone - trabeculae
• covered by compact bone
• found in heads of long bones and in middle of flat bones such as the
sternum
– compact bone – denser calcified tissue with no visible spaces
• more complex arrangement
• cells and matrix surround vertically oriented blood vessels in long
bones
Bone Tissue (compact bone)
Concentric
Central
lamellae
Lacunae Canaliculi of osteon canal Osteon
(a)
Blood
vessel
(a)
•
(b)
Adipocyte Lipid in
nucleus
adipocyte
(b)
most compact bone is arranged in cylinders that surround central (haversian
or osteonic) canals that run longitudinally through shafts of long bones
– blood vessels and nerves travel through central canal
•
bone matrix deposited in concentric lamella
– onionlike layers around each central canal
•
•
•
•
osteon – central canal and its surrounding lamellae
osteocytes – mature bone cells that occupy the lacunae
canaliculi – delicate canals that radiate from each lacuna to its neighbors, and
allows osteocytes to contact each other
periosteum – tough fibrous connective tissue covering of the bone as a whole
Others: bone (osseous tissue)
Description: Hard, calcified
matrix containing many collagen
fibers; osteocytes lie in lacunae.
Very well vascularized.
Function: Supports and protects
(by enclosing); provides levers for
the muscles to act on; stores
calcium and other minerals and
fat; marrow inside bones is the
site for blood cell formation
(hematopoiesis).
Central
canal
Lacunae
Lamella
Location: Bones
Photomicrograph: Cross-sectional view
of bone (125x).
Blood
•
fluid connective tissue
•
transports cells and dissolved
matter from place to place
•
plasma – blood’s liquid
ground substance
•
formed elements – cells and
cell fragments
– erythrocytes – red blood
cells – transport O2 and CO2
– leukocytes – white blood
cells – defense against
infection and other diseases
– platelets – cell fragments
involved in clotting and other
mechanisms
Platelets
Neutrophils
Lymphocyte
Erythrocytes
Monocyte
Connective tissue: blood
Description: Red and white blood
cells in a fluid matrix (plasma).
Red blood
cells
(erythrocytes)
Function: Transport respiratory
gases, nutrients, wastes, and other
substances.
White blood
cells:
• Lymphocyte
• Neutrophil
Location: Contained within blood
vessels.
Plasma
Photomicrograph: Smear of human blood
(1670x); shows two white blood cells
surrounded by red blood cells.
Cartilage
•
supportive connective tissue with flexible, rubbery matrix
•
gives shape to ear, tip of nose, and larynx
•
chondroblasts produce matrix and surround them selves until
they become trapped in little cavities (lacunae)
•
chondrocytes – cartilage cells in lacunae
•
perichondrium – sheath of dense irregular connective tissue
that surrounds elastic and most hyaline cartilage (not articular
cartilage)
– contains a reserve population of chondroblasts that contribute to
cartilage growth throughout life
•
No blood vessels
– diffusion brings nutrients and removes wastes
– heals slowly
•
matrix rich in chondroitin sulfate and contain collagen fibers
•
types of cartilage vary with fiber types
– hyaline cartilage, fibrocartilage and elastic cartilage
Hyaline Cartilage
Matrix
(a)
•
•
•
•
Cell
nest Perichondrium
Lacunae
Chondrocytes
(b)
clear, glassy microscopic appearance because of unusual
fineness of the collagen fibers
usually covered by perichondrium
articular cartilage, costal cartilage, trachea, larynx, fetal skeleton
eases joint movement, holds airway open, moves vocal cords during
speech
Cartilage: hyaline
Description: Amorphous but firm
matrix; collagen fibers form an
imperceptible network;
chondroblasts produce the matrix
and when mature (chondrocytes)
lie in lacunae.
Function: Supports and reinforces;
serves as resilient cushion; resists
compressive stress.
Chondrocyte
in lacuna
Location: Forms most of the
embryonic skeleton; covers the
ends of long bones in joint cavities;
forms costal cartilages of the ribs;
cartilages of the nose, trachea, and
larynx.
Costal
cartilages
Matrix
Photomicrograph: Hyaline cartilage from
a costal cartilage of a rib (470x).
Elastic Cartilage
Perichondrium
Elastic
fibers
Lacunae
Chondrocytes
(a)
Blood
vessel
(a)
(b)
(b)
• cartilage containing elastic fibers
• covered with perichondrium
• provides flexible, elastic support
– external ear and epiglottis
Adipocyte Lipid in
nucleus
adipocyte
Elastic Cartilage
Cartilage: elastic
Description: Similar to hyaline
cartilage, but more elastic fibers
in matrix.
Function: Maintains the shape of
a structure while allowing great
flexibility.
Chondrocyte
in lacuna
Matrix
Location: Supports the external
ear (pinna); epiglottis.
Photomicrograph: Elastic cartilage from
the human ear pinna; forms the flexible
skeleton of the ear (800x).
Fibrocartilage
Collagen
fibers
(a)
(a)
(a)
Blood
Adipocyte Lipid in
Blood
Adipocyte Lipid in
vessel
nucleus
adipocyte
vessel
nucleus
adipocyte
(b)
(b)
•
•
•
Chondrocytes
(b)
cartilage containing large, coarse bundles of collagen fibers
never has perichondrium
resists compression and absorbs shock
– pubic symphysis, menisci, and intervertebral discs
Fibrocartilage
Cartilage: fibrocartilage
Description: Matrix similar to but
less firm than that in hyaline
cartilage; thick collagen fibers
predominate.
Function: Tensile strength allows
it to absorb compressive shock.
Location: Intervertebral discs;
pubic symphysis; discs of knee
joint.
Chondrocytes
in lacunae
Intervertebral
discs
Collagen
fiber
Photomicrograph: Fibrocartilage of an
intervertebral disc (125x). Special staining
produced the blue color seen.
Adipose Tissue / Another Form of CT
•
adipose tissue (fat) – tissue in which adipocytes are the
dominant cell type
•
space between adipocytes is occupied by areolar tissue,
reticular tissue, and blood capillaries
•
fat is the body’s primary energy reservoir
•
the quantity of stored triglyceride and the number of
adipocytes are quite stable in a person
–
–
–
fat is recycled continuously to prevent stagnation
new triglycerides are constantly synthesized and stored
old triglycerides are hydrolyzed and released into circulation
•
provides thermal insulation
•
anchors and cushions organs such as eyeball, kidneys
•
contributes to body contours – female breast and hips
•
on average, women have more fat than men
•
too little fat can reduce female fertility
•
most adult fat is called white fat
•
brown fat – in fetuses, infants, children – a heat generating
tissue
Adipose Tissue
Blood
vessel
(a)
Adipocyte
nucleus
Lipid in
adipocyte
(b)
• 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
Connective tissue proper: loose connective tissue, adipose
Description: Matrix as in areolar,
but very sparse; closely packed
adipocytes, or fat cells, have
nucleus pushed to the side by
large fat droplet.
Function: Provides reserve food
fuel; insulates against heat loss;
supports and protects organs.
Nucleus of
adipose
(fat) cell
Location: Under skin in
subcutaneous tissue; around
kidneys and eyeballs; within
abdomen; in breasts.
Adipose
tissue
Fat droplet
Photomicrograph: Adipose tissue from
the subcutaneous layer under the skin (350x).
Mammary
glands
Excitable Tissues
Muscular & Nervous Tissue
• excitability – a characteristic of all living cells
– developed to highest degree in nervous and muscular
tissues
• membrane potential – electrical charge
difference (voltage) that occurs across the
plasma membranes is the basis for their
excitation
– respond quickly to outside stimulus by means of
changes in membrane potential
• nerves – changes result in rapid transmission of signals
to other cells
• muscles – changes result in contraction, shortening of
the cell
•
specialized for communication by
electrical and chemical signals
•
consists of neurons (nerve cells)
– detect stimuli
– respond quickly
– transmit coded information rapidly to
other cells
•
neuroglia (glial)
– protect and assist neurons
– ‘housekeepers’ of nervous system
•
neuron parts
– neurosoma (cell body)
• houses nucleus and other organelles
• cell’s center of genetic control and
protein synthesis
– dendrites
• multiple short, branched processes
• receive signals from other cells
• transmit messages to neurosoma
– axon (nerve fiber)
• sends outgoing signals to other cells
• can be more than a meter long
Nervous Tissue
Nuclei of glial cells
Axon
Neurosoma
Dendrites
Nervous tissue
Description: Neurons are
branching cells; cell processes
that may be quite long extend from
the nucleus-containing cell body;
also contributing to nervous tissue
are nonexcitable supporting cells.
Nuclei of
supporting
cells
Neuron processes Cell body
Axon Dendrites
Cell body
of a neuron
Function: Neurons transmit
electrical signals from sensory
receptors and to effectors (muscles
and glands) which control their
activity; supporting cells support
and protect neurons.
Neuron
processes
Location: Brain, spinal
cord, and nerves.
Photomicrograph: Neurons (350x).
Muscular Tissue
• elongated cells that are specialized to
contract in response to stimulation
• primary job is to exert physical force on
other tissues and organs
• creates movements involved in body and
limb movement, digestion, waste
elimination, breathing, speech, and blood
circulation
• important source of body heat
• three types of muscle: skeletal, cardiac,
and smooth
Skeletal Muscle
•
•
•
long, threadlike cells – muscle fibers
most attach to bone
exceptions – in tongue, upper esophagus, facial muscles,
some sphincter muscles – (ringlike or cufflike muscles that
open and close body passages)
•
•
•
contains multiple nuclei adjacent to plasma membrane
striations – alternating dark and light bands
voluntary – conscious control over skeletal muscles
Nuclei
(a)
(b)
Striations
Muscle fiber
Skeletal muscle
Description: Long, cylindrical,
multinucleate cells; obvious
striations.
Part of
muscle
fiber (cell)
Function: Voluntary movement;
locomotion; manipulation of the
environment; facial expression;
voluntary control.
Nuclei
Location: In skeletal muscles
attached to bones or occasionally
to skin.
Striations
Photomicrograph: Skeletal muscle
(approx. 440x). Notice the obvious banding
pattern and the fact that these large cells are
multinucleate.
Cardiac Muscle
•
•
•
•
limited to the heart
myocytes or cardiocytes are much shorter, branched,
and notched at ends
contain one centrally located nucleus surrounded by
light staining glycogen
intercalated discs join cardiocytes end to end
– provide electrical and mechanical connection
•
striated, and involuntary (not under conscious control)
Intercalated discs
(a)
(b)
Striations
Glycogen
Cardiac muscle
Description: Branching, striated,
generally uninucleate cells that
interdigitate at specialized
junctions (intercalated discs).
Intercalated
discs
Function: As it contracts, it
propels blood into the circulation;
involuntary control.
Striations
Location: The walls of the heart.
Nucleus
Photomicrograph: Cardiac muscle (900x);
notice the striations, branching of cells, and
the intercalated discs.
Smooth Muscle
Nuclei
(a)
•
•
•
•
•
Muscle cells
(b)
lacks striations and is involuntary
relatively short, fusiform cells (thick in middle, tapered at ends)
one centrally located nucleus
visceral muscle – forms layers of digestive, respiratory, and urinary tract:
blood vessels, uterus and other viscera
propels contents through an organ, regulates diameter of blood vessels
Smooth muscle
Description: Spindle-shaped
cells with central nuclei; no
striations; cells arranged closely
to form sheets.
Function: Propels substances or
objects (foodstuffs, urine, a baby)
along internal passageways;
involuntary control.
Nuclei
Location: Mostly in the walls of
hollow organs.
Smooth
muscle
cell
Photomicrograph: Sheet of smooth
muscle (720x).
Membranes
•
Functions:
– Covers the exterior body surface
– line body cavities
– cover the viscera
•
serous membrane (serosa) - internal membrane
– simple squamous epithelium over areolar tissue
– produces serous fluid that arises from blood
– covers organs and lines walls of body cavities
• endothelium lines blood vessels and heart
• mesothelium line body cavities (pericardium, peritoneum and pleura)
•
Mucous membranes
– Line cavities and tubular structures “continuous” with external environment
•
cutaneous membrane
– the skin = largest membrane in the body
– stratified squamous epithelium (epidermis) over connective tissue (dermis)
– relatively dry layer serves protective function
•
synovial membrane - lines joint cavities
– connective tissue layer only, secretes synovial fluid
Serous Membranes
• Serosae—found in closed ventral
body cavity
• Simple squamous epithelium
(mesothelium) resting on thin
areolar connective tissue
• Parietal serosae line internal body
cavity walls
• Visceral serosae cover internal
organs
• Serous fluid between layers
• Moist membranes
• Pleurae, pericardium, peritoneum
Serous membranes
Serous membranes line body cavities that are
closed to the exterior.
Parietal
pleura
Visceral
pleura
Visceral
Parietal
pericardium pericardium
Parietal
peritoneum
Visceral
peritoneum
Mucous Membranes
• Mucosa indicates location not cell
composition
• All called mucosae
– Line body cavities open to the exterior (e.g.,
Digestive, respiratory, urogenital tracts)
• Moist membranes bathed by secretions (or
urine)
• Epithelial cells of mucous membranes
over layer of connective tissue called
lamina propria (form of areolar tissue)
• May secrete mucus
– Mucin + water = mucus
Mucous membranes
Mucous membranes line body
cavities that are open to the
exterior.
Mucosa of
nasal cavity
Mucosa of
mouth
Esophagus
lining
Mucosa of
lung bronchi
Mucous coat
Cilia
Epithelium
Mucin in
goblet cell
Ciliated cells of
pseudostratified
epithelium
Basement
membrane
Mucous
membrane
(mucosa)
Blood vessel
Lamina
propria
Collagen fibers
Fibroblast
Elastic fibers
Muscularis
mucosae
• Mucous Membranes (Mucosa)
– lines passages that open to the external environment
– digestive, respiratory, urinary, and reproductive tracts
– consists of two to three layers:
• epithelium
• lamina propria – areolar connective tissue
• muscularis mucosae – smooth muscle layer
– absorptive, secretory, and protective functions
– covered with mucus
Intracelluar
Junctions
Intercellular Junctions
Tight junction
Plasma membrane
Membrane protein
Intercellular space
Desmosome
Intermediate filaments
Glycoprotein
Protein plaque
Intercellular space
Plasma membrane
Gap junction
Pore
Connexon
Membrane
protein
Cell nucleus
Basement membrane
Hemidesmosome
Pore
Proteins
•
•
•
intercellular junctions – connections between one cell and
another
all cells (except blood and metastatic cancer cells) are anchored to
each other or their matrix by intercellular junctions
resist stress and communicate with each other
Tight Junctions
• a region in which adjacent cells are bound together by
fusion of the outer phospholipid layer of their plasma
membranes.
– in epithelia, forms a zone that complete encircles each cell near
its apical pole
– seals off intercellular space
– makes it impossible for something to pass between cells
Tight junction
Desmosome
Gap junction
Desmosomes
•
•
•
patch that holds cells together (like a clothing snap)
serves to keep cells from pulling apart – resists mechanical
stress
hooklike J-shaped proteins arise from cytoskeleton
– approach cells surface
– penetrate into thick protein plaques linked to transmembrane
proteins
•
hemidesmosomes – anchor the basal cells of epithelium
to the underlying basement membrane
– epithelium can not easily peel away from underlying tissues
Tight junction
Desmosome
Gap junction
Gap Junctions
•
formed by a ringlike connexon
•
communicating junction
– consists of six transmembrane proteins arranged like segments of an
orange
– surrounding a water-filled pores
– ions, glucose, amino acids and other solutes pass from one cell to the
next
Tight junction
Desmosome
Gap junction