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Ingegneria delle tecnologie
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Anatomia umana
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Lezione 3. Cenni di embriologia
ed istologia generale.
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THE TISSUE LEVEL OF ORGANIZATION
After studying this chapter, you will be able to:
• Identify the main tissue types and discuss their roles in the human body
• Identify the four types of tissue membranes and the characteristics of each that make them functional
• Explain the functions of various epithelial tissues and how their forms enable their functions
• Explain the functions of various connective tissues and how their forms enable their functions
• Describe the characteristics of muscle tissue and how these enable function
• Discuss the characteristics of nervous tissue and how these enable information processing and control
of muscular and glandular activities
 our body: at least 200 distinct cell types.
 same internal structures but vary enormously
in shape and function.
 occur in organized layers: tissue
 starts as a single cell at fertilization and it
gives rise to trillions of cells, each built from
the same blueprint, but organizing into tissues
and becoming irreversibly committed to a
developmental pathway.
Types of Tissues
Tissue = a group of cells found
together in the body, that share a
common and morphological features
and are arranged in an orderly pattern
that achieves the tissue’s functions.
many types of cells but organized into
4 broad categories of tissues:
1. epithelial,
2. connective,
3. muscle
4. nervous
with a specific functions that
contribute to the overall health and
maintenance of the body.
Histology = microscopic study of
tissue appearance, organization, and
function.
Tissue Preparation—Light Microscopy
Histology is a visual, as well as a
very colorful, science that is
studied with the aid of a light micro
scope. The prepared specimens for
examination are thinly sliced,
placed on a glass slide, stained
with a variety of stains, and
examined with a light microscope
via a light beam that passes
through the tissues that are fixed
on the slide.
Antonie van
Leeuwenhoek (1632–
1724) is credited with
bringing the
microscope to the
attention of biologists
Tissue Preparation—Light Microscopy
FIXATION
= prompt immersion of the specimen with
different chemical solutions, to preserve a
section of tissue or organ for histologic
examination
 essential in order to permanently
preserve structural and molecular
composition of specimen.
 to further accelerate penetration and
proper
fixation
process,
tissue
specimen is first cut into small pieces
and then immersed into fixative.
 hardens specimen for sectioning,
causes
cross-linkage
of
macromolecules
within
the
cells,
reduces
cellular
degeneration,
preserves integrity of cells and tissues,
and increases their affinity to take up
different stains.
 most commonly used fixative for light
microcopy
is
neutral-buffered
FORMALDEHYDE.
Aldehyde fixatives form crosslinks between proteins.
Tissue Preparation—Light Microscopy
POSTFIXATION
 After fixation, water must first be removed by
passing it through a series of ascending ALCOHOL
(ethanol) concentrations, usually from 70 to 100%
 then specimen must be cleared of alcohol by
passing it through several changes of such clearing
agents as XYLENE
 Once the specimen is impregnated with the clearing
agent xylene, it is then placed in a warm mold
containing melted PARAFFIN. Once removed from
the heat source, the paraffin in the mold cools,
solidifies, and encases the specimen.
 paraffin block then trimmed to the size of the
specimen and mounted in an instrument called a
MICROTOME [precisely advances the paraffin block
so that the sections are cut at specific and
predetermined increments with a steel knife] =
sections are normally cut at 3-10 μm thickness.
 thin paraffin sections are then collected and floated
in a warm water bath and placed onto a glass slide
that has been covered with a thin layer of albumen,
which serves as an adhesive medium for the
specimen.
Staining of Sections
 paraffin sections on the glass slide
are colorless  needs to be
stained.
 paraffin must first be dissolved
from the specimen with solvents,
such as xylene, and the sections
rehydrated with a series of
decreasing alcohol concentrations.
 hydrated sections can then be
stained with a variety of watersoluble stains, which selectively
stain various components of the
specimen
 Most of the stains used for
histologic slide preparations act
like acidic or basic compounds:
structures that stain most readily
with basic stains are called
BASOPHILIC, and those that stain
with acidic stains are called
ACIDOPHILIC
[most
common
stains are hematoxylin and eosin
stains]
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Staining of Sections
Transmission and Scanning Electron Microscopy
Interpretation of Histologic Sections
the most challenging and difficult aspects of histology:
interpretation of what the two-dimensional histology
sections represent in three dimensions.
Histologic sections = thin, flat slices of fixed and stained
tissues or organs mounted on flat glass slides.
sections normally composed of cellular, fibrous, and
tubular structures cut in different planes  variety of
shapes, sizes, and layers may be visible, depending on
the plane of section.
Fibrous structures are solid and are found in connective,
nervous, and muscle tissues.
Tubular structures are hollow and represent various types
of blood vessels, lymph vessels, glandular ducts, and
glands of the body.
Planes of Section of a Round, Solid Object
Planes of Section Through a Hollow Structure or a
Tube
Planes of Section Through a Hollow Structure or a
Tube
Cell microscopic anatomy (TEM)
Ciliated and nonciliated cells
Junctional complex
Basal region
Basal region in ions transporting cell
Cilia and microvilli
Nuclear envelope and pores
Mitochondria
RER
SER
Golgi apparatus
Lysosomes
Mitosis
The 4 Types of Tissues
1. Epithelial tissue (epithelium) = sheets
of cells that cover exterior surfaces of
the body, internal cavities and
passageways, and forms certain
glands.
2. Connective tissue = binds cells and
organs together (functions in the
protection, support, and integration of
all parts of the body)
3. Muscle tissue = excitable, responding
to stimulation and contracting to provide
movement, and occurs as 3 major
types: skeletal (voluntary) muscle,
smooth muscle, and cardiac muscle in
the heart.
4. Nervous tissue = also excitable,
allowing the propagation of
electrochemical signals in the form of
nerve impulses .
The 4 Types of Tissues
Organs are made of many different tissues…of the 4
fundamental types
sections
through 4
different
organs:
Intestines, Skin,
Lung, & Trachea.
(each organ is
made of multiple
tissues and that
their are
variations on
how the tissues
are designed)
Embryonic Origin of Tissues
totipotent
three major cell lineages
established within the embryo
Embryonic Origin of Tissues
3 lineages of embryonic cells forms 3
distinct germ layers identified by its
relative position:
1. ectoderm (ecto-= “outer”),
2. mesoderm (meso- = “middle”),
3. endoderm (endo- = “inner”).
Embryonic Origin of Tissues
!!! epithelial tissue
originates in all
three layers,
whereas nervous
tissue derives
primarily from the
ectoderm and
muscle tissue from
mesoderm.
Tissue Membranes
Tissue membrane = thin layer or sheet of
cells that covers the outside of the body (for
example, skin), the organs (for example,
pericardium), internal passageways that lead
to the exterior of the body (for example,
abdominal mesenteries), and the lining of the
moveable joint cavities.
2 basic types
1. connective tissue
2. epithelial membranes
Tissue Membranes
1. Connective Tissue Membranes = formed solely from connective
tissue, encapsulate organs, and line our movable joints (synovial
membrane)
2. Epithelial Membranes = composed of epithelium attached to a
layer of connective tissue
i. mucous membrane (mucosae) = line the body cavities and hollow
passageways that open to the external environment, and include the
digestive, respiratory, excretory, and reproductive tracts. Mucous,
produced by the epithelial exocrine glands, covers the epithelial layer.
The underlying connective tissue, called the lamina propria, supports
the epithelial layer.
ii. serous membrane = composed of mesodermally derived epithelium
called the mesothelium that is supported by connective tissue, line
coelomic cavities (do not open to outside).
iii. cutaneous membrane (skin) = stratified squamous epithelial membrane
resting on top of connective tissue.
Epithelial Tissue
= essentially large sheets of cells covering all the surfaces of the body exposed to the outside
world + lining the outside of organs + much of the glandular tissue of the body;
share structural/ functional features:
 highly cellular, with little or no extracellular
matrix between cells
 cell junction = specialized intercellular
connection between cell
 polarity = differences in structure and function
between the exposed or apical facing surface
of the cell and the basal surface
 basal lamina = (a mixture of glycoproteins and
collagen) provides an attachment site for the
epithelium, separating it from underlying
connective tissue and attaches to a reticular
lamina, which is secreted by the underlying
connective tissue, forming a basement
membrane that hold it all together.
 nearly completely avascular.
 capable of rapidly replacing damaged and dead
cells.
Epithelial Tissue
Generalized Functions of Epithelial Tissue
• provide the body’s first line of protection from physical, chemical, and biological wear and
tear, controlling permeability and allowing selective transfer of materials across a physical
barrier
• are sometimes capable of secretion and release mucous and specific chemical compounds
onto their apical surfaces.
The Epithelial Cell
typically characterized by the polarized distribution of organelles and membranebound proteins between their basal and apical surfaces: certain organelles are
segregated to the basal sides, whereas other organelles and extensions, such as cilia
(microscopic extensions of the apical cell membrane that are supported by
microtubules), when present, are on the apical surface and beat in unison and move
fluids as well as trapped particles.
Epithelial Tissue
Cell to Cell
Junctions
Cells of epithelia are closely
connected
and
are
not
separated by extracellular
material. 3 basic types of
connections allow varying
degrees of interaction between
the cells:
1. tight junctions,
2. anchoring junctions,
3. gap junctions
Epithelial Tissue
Classification of
Epithelial Tissues
classified according to the shape
of the cells and number of the cell
layers formed. Transitional
describes a form of specialized
stratified epithelium in which the
shape of the cells can vary.
Epithelial Tissue
Classification of Epithelial Tissues
classified according to the shape of the cells and number of the cell layers
formed. Transitional describes a form of specialized stratified epithelium in
which the shape of the cells can vary.
Epithelial Tissue
goblet cell
Both simple and pseudostratified columnar epithelia
are heterogeneous epithelia because they include
additional types of cells interspersed among the
epithelial cells.
For example, a goblet cell is a mucous-secreting
unicellular “gland” interspersed between the
columnar epithelial cells of mucous membranes
Epithelial Tissue
different
categories of
epithelial cell
tissue cells
Epithelial Tissue
different categories
tissue cells
of
epithelial
cell
Epithelial Tissue
Glandular Epithelium
gland = a structure made up of one or more cells modified to
synthesize and secrete chemical substances; most glands consist of
groups of epithelial cells.
1. Endocrine Glands
a ductless gland that releases secretions (hormones) directly into
surrounding tissues and fluids (endo- = “inside”), that are part of
regulatory system
2. Exocrine Glands
gland whose secretions leave through a duct that opens directly, or
indirectly, to the external environment (exo- = “outside”). through a
tubular duct that leads to the epithelial surface
Epithelial Tissue
Exocrin Glandular
Structure
Exocrine glands classified:
• unicellular = scattered
single cells (goblet
cells)
• multicellular
(classified
by
structure)
Epithelial Tissue
Exocrin
Glandular
Methods and Types of
Secretion
Exocrine glands classified
• mode of secretion
• nature of the substances
released
serous gland  watery, bloodplasma-like secretions
mucous gland  watery to
viscous products rich in the
glycoprotein mucin.
mixed glands  both serous and
mucous glands and release both
types of secretions.
Epithelial Tissue
Sebaceous Glands
secrete oils that lubricate and protect the skin and
are holocrine glands (are destroyed after releasing their contents, new
glandular cells form to replace the cells that are lost).
Epithelial Tissue
Type of Tissue
Pseudostratified columnar
Function
Location
removing dust and particles from lines the respiratory
airways, has cilia
passageways
Epithelial Tissue
Simple Columnar
Absorption
lines the uterus and most
organs of the digestive tract
Epithelial Tissue
Simple Cuboidal
Secretion and Absorption
glands, kidney tubules,
ovaries
Epithelial Tissue
Simple Squamous
Diffusion and Filtration
lungs, walls of capillaries and
vessels
Epithelial Tissue
Stratified Squamous
Protects underlying cells
skin(keratinized) and the
throat, vagina, mouth (soft)
Epithelial Tissue
Stratified Cuboidal
Protection
lines ducts of the mammary
glands, sweat glands,
pancreas
Epithelial Tissue
Stratified Columnar
Protection, secretion
male urethra and vas
deferens, parts of the
pharynx
Epithelial Tissue
Transitional (unstretched)
Specialized to become distended
urinary tract
Connective Tissue
General structure of CT
 cells are dispersed in a matrix
 matrix = a large amount of extracellular
material produced by the CT cells and plays a
major role in the functioning
 matrix component = ground substance often
crisscrossed by protein fibers
 ground substance usually fluid, but it can also
be mineralized and solid (bones)
 CTs = vast variety of forms, but typically 3
characteristic
components:
cells,
large
amounts of amorphous ground substance,
and protein fibers.
Connective Tissue
GROUND SUBSTANCE
In connective tissue, the ground substance is
an amorphous gel-like substance surrounding
the cells. In a tissue, cells are surrounded and
supported by an extracellular matrix. Ground
substance traditionally does not include fibers
(collagen and elastic fibers), but does include
all the other components of the extracellular
matrix.
The components of the ground substance vary
depending on the tissue. Ground substance is
primarily composed of water,
glycosaminoglycans (most notably
hyaluronan), proteoglycans, and glycoproteins.
Usually it is not visible on slides, because it is
lost during the preparation process.
Connective Tissue
Functions of Connective Tissues
 Support and connect other tissues
 Protection (fibrous capsules and bones that protect delicate organs and, of course, the
skeletal system).
 Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized
fluid connective tissues, such as blood and lymph.
 Adipose cells store surplus energy in the form of fat and contribute to the thermal
insulation of the body.
Embryonic Connective Tissue
All connective tissues derive from the mesodermal layer of the embryo.
The first connective tissue to develop in the embryo is mesenchyme, the stem cell line from
which all connective tissues are later derived. Clusters of mesenchymal cells are scattered
throughout adult tissue and supply the cells needed for replacement and repair after a
connective tissue injury.
A second type of embryonic connective tissue forms in the umbilical cord, called mucous
connective tissue or Wharton’s jelly. This tissue is no longer present after birth, leaving only
scattered mesenchymal cells throughout the body.
Connective Tissue
Classification of CTs
3 broad categories of CT are classified according to the characteristics of their ground
substance and the types of fibers found within the matrix
Connective Tissue
Connective Tissue Proper
CELLS
 Fibroblasts present in all CT proper
 Fibrocytes, adipocytes, and mesenchymal cells are fixed cells (remain
within the connective tissue).
 Other cells move in and out in response to chemical signals: macrophages,
mast cells, lymphocytes, plasma cells, and phagocytic cells (actually part of
the immune system)
Connective Tissue
Connective Tissue Proper
Connective Tissue Fibers and Ground Substance
fibroblasts)
(all secreted by
3 main types :
• Collagen fiber = made from fibrous protein subunits linked together to form a
long and straight fiber, while flexible, have great tensile strength, resist
stretching, and give ligaments and tendons their characteristic resilience and
strength.
• Elastic fiber = protein elastin (that after being stretched or compressed, it will
return to its original shape) along with lesser amounts of other proteins and
glycoproteins.
• Reticular fiber = also formed from the same protein subunits as collagen fibers,
but arrayed in a branching network.
• All of these fibers embedded in ground substance = made of polysaccharides,
specifically hyaluronic acid, and proteins (combined to form a proteoglycan
with a protein core and polysaccharide branches). The proteoglycan attracts
and traps available moisture forming a clear, viscous, colorless matrix.
Connective Tissue
Connective Tissue Proper
Loose Connective Tissue
found between many organs where it acts both to absorb shock and bind tissues
togethe + allows water, salts, and various nutrients to diffuse through to adjacent
or imbedded cells and tissues.
1. Adipose tissue = mostly of fat storage cells, with little extracellular matrix.
White fat contributes mostly to lipid storage and can serve as insulation from cold
temperatures and mechanical injuries. Brown adipose tissue is more common in
infants (“baby fat”) and is thermogenic
Connective Tissue
Connective Tissue Proper
Loose Connective Tissue
2. Areolar tissue shows little specialization and fills the spaces between muscle
fibers, surrounds blood and lymph vessels, and supports organs in the abdominal
cavity. Areolar tissue underlies most epithelia and represents the connective tissue
component of epithelial membranes.
3. Reticular tissue = mesh-like, supportive framework for soft organs such as
lymphatic tissue, spleen, and liver.
Connective Tissue
Supportive
Connective Tissues
allow the body to maintain its posture and
protect internal organs + 2 major forms:
1. Cartilage
The distinctive appearance of cartilage is due to
polysaccharides called chondroitin sulfates, which
bind with ground substance proteins to form
proteoglycans. Embedded within the cartilage
matrix are chondrocytes and the space they occupy
are called lacunae (singular = lacuna). A layer of
dense
irregular
connective
tissue,
the
perichondrium, encapsulates the cartilage.
avascular very slow healing. 3 main types:
2. Bone
the hardest CT with rigid extracellular matrix
contains mostly collagen fibers embedded in a
mineralized
ground
substance
containing
hydroxyapatite. Osteocytes are located within
lacunae. highly vascularized tissue.
Connective Tissue
Fluid Connective Tissue
= blood and lymph where cells circulate in a liquid extracellular matrix
Connective Tissue
The following types of connective tissue are covered in this activity:
1.
Loose (areolar) connective tissue (delicate thin layers between
tissues; present in all mucous membranes)
2. Adipose tissue (fat)
3. Dense connective tissue (tendons/ligaments)
4. Hyaline cartilage (nose/ends of long bones/ribs)
5. Elastic cartilage (outer ear/epiglottis)
6. Fibrocartilage (between vertebrae/knee joints/pubic joint)
7. Bone (skeletal system)
8
Blood (bloodstream)
Connective Tissue
Table 4.1 Comparison of Classes of Connective Tissues (1 of 2)
Connective Tissue
Table 4.1 Comparison of Classes of Connective Tissues (2 of 2)
Figure 4.8a Connective tissues.
(a) 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.
Elastic
fibers
Function: Wraps and cushions
organs; its macrophages phagocytize
bacteria; plays important role in
inflammation; holds and conveys
tissue fluid.
Collagen
fibers
Location: Widely distributed under
epithelia of body, e.g., forms lamina
propria of mucous membranes;
packages organs; surrounds
capillaries.
Fibroblast
nuclei
Epithelium
Lamina
propria
Copyright © 2010 Pearson Education, Inc.
Photomicrograph: Areolar connective tissue, a
soft packaging tissue of the body (300x).
Figure 4.7 Areolar connective tissue: A prototype (model) connective tissue.
Cell types
Macrophage
Extracellular
matrix
Ground substance
Fibers
• Collagen fiber
• Elastic fiber
• Reticular fiber
Fibroblast
Lymphocyte
Fat cell
Mast cell
Neutrophil
Copyright © 2010 Pearson Education, Inc.
Capillary
Figure 4.8b Connective tissues.
(b) 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
fat cell
Location: Under skin in the
hypodermis; around kidneys and
eyeballs; within abdomen; in breasts.
Vacuole
containing
fat droplet
Adipose
tissue
Mammary
glands
Copyright © 2010 Pearson Education, Inc.
Photomicrograph: Adipose tissue from the
subcutaneous layer under the skin (350x).
Figure 4.8c Connective tissues.
(c) 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).
Reticular
fibers
Spleen
Photomicrograph: Dark-staining network of reticular
connective tissue fibers forming the internal skeleton
of the spleen (350x).
Copyright © 2010 Pearson Education, Inc.
Figure 4.8d Connective tissues.
(d) Connective tissue proper: dense connective tissue, dense regular
Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.
Collagen
fibers
Function: Attaches muscles to
bones or to muscles; attaches bones
to bones; withstands great tensile
stress when pulling force is applied
in one direction.
Location: Tendons, most
ligaments, aponeuroses.
Nuclei of
fibroblasts
Shoulder
joint
Ligament
Photomicrograph: Dense regular connective
tissue from a tendon (500x).
Tendon
Copyright © 2010 Pearson Education, Inc.
Figure 4.8e Connective tissues.
(e) Connective tissue proper: dense connective tissue, dense irregular
Description: Primarily
irregularly arranged collagen
fibers; some elastic fibers;
major cell type is the fibroblast.
Nuclei of
fibroblasts
Function: Able to withstand
tension exerted in many
directions; provides structural
strength.
Location: Fibrous capsules of
organs and of joints; dermis of
the skin; submucosa of
digestive tract.
Fibrous
joint
capsule
Copyright © 2010 Pearson Education, Inc.
Collagen
fibers
Photomicrograph: Dense irregular
connective tissue from the dermis of the
skin (400x).
Figure 4.8f Connective tissues.
(f) Connective tissue proper: dense connective tissue, elastic
Description: Dense regular
connective tissue containing a high
proportion of elastic fibers.
Function: Allows recoil of tissue
following stretching; maintains
pulsatile flow of blood through
arteries; aids passive recoil of lungs
following inspiration.
Elastic fibers
Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within the
walls of the bronchial tubes.
Aorta
Heart
Copyright © 2010 Pearson Education, Inc.
Photomicrograph: Elastic connective tissue in
the wall of the aorta (250x).
Figure 4.8g Connective tissues.
(g) 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;
has resilient cushioning properties;
resists compressive stress.
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.
Chondrocyte
in lacuna
Matrix
Costal
cartilages
Copyright © 2010 Pearson Education, Inc.
Photomicrograph: Hyaline cartilage from the
trachea (750x).
Figure 4.8h Connective tissues.
(h) 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
Location: Supports the external
ear (pinna); epiglottis.
Matrix
Photomicrograph: Elastic cartilage from
the human ear pinna; forms the flexible
skeleton of the ear (800x).
Copyright © 2010 Pearson Education, Inc.
Figure 4.8i Connective tissues.
(i) Cartilage: fibrocartilage
Description: Matrix similar to
but less firm than that in hyaline
cartilage; thick collagen fibers
predominate.
Function: Tensile strength
with the ability 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.
Copyright © 2010 Pearson Education, Inc.
Figure 4.8j Connective tissues.
(j) Others: bone (osseous tissue)
Description: Hard, calcified
matrix containing many collagen
fibers; osteocytes lie in lacunae.
Very well vascularized.
Central
canal
Function: Bone 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).
Lacunae
Lamella
Location: Bones
Photomicrograph: Cross-sectional view
of bone (125x).
Copyright © 2010 Pearson Education, Inc.
Figure 4.8k Connective tissues.
(k) Others: blood
Description: Red and white
blood cells in a fluid matrix
(plasma).
Plasma
Function: Transport of
respiratory gases, nutrients,
wastes, and other substances.
Location: Contained within
blood vessels.
Neutrophil
Red blood
cells
Lymphocyte
Photomicrograph: Smear of human blood (1860x); two
white blood cells (neutrophil in upper left and lymphocyte
in lower right) are seen surrounded by red blood cells.
Copyright © 2010 Pearson Education, Inc.
Connective Tissue
EXAMPLES
Can you name?
First, the tissue type
Second, where in the body the tissue is found
Connective Tissue
What kind of tissue does this represent?
Loose (areolar) connective tissue
Where in the body can you find this tissue?
delicate thin layers between tissues; present in all mucous membranes
Connective Tissue
What kind of tissue does this represent?
Adipose tissue
Where in the body can you find this tissue?
fat
Connective Tissue
What kind of tissue does this represent?
Dense connective tissue
Where in the body can you find this tissue?
tendons; ligaments
Connective Tissue
What kind of tissue does this represent?
Hyaline cartilage
Where in the body can you find this tissue?
nose; ends of long bones; ribs
Connective Tissue
What kind of tissue does this represent?
Elastic cartilage
Where in the body can you find this tissue?
outer ear; epiglottis
Connective Tissue
What kind of tissue does this represent?
Fibrocartilage
Where in the body can you find this tissue?
between vertebrae; knee joints; pubic joint
Connective Tissue
What kind of tissue does this represent?
Bone
Where in the body can you find this tissue?
skeletal system
Connective Tissue
What kind of tissue does this represent?
Blood
Where in the body can you find this tissue?
bloodstream
Muscle Tissue
• characterized by properties that allow movement.
• muscle cells are excitable (=respond to a stimulus) + contractile (=can shorten and
generate a pulling force)
• some muscle movement is voluntary (=under conscious control) other involuntary
(ie contraction of your pupil)
• classified into 3 types according to structure and function
Muscle Tissue
• Skeletal
muscle
makes
possible
locomotion, facial expressions, posture,
and other voluntary movements (40%
body mass), participate in thermal
homeostasis: myocyte (from myoblasts,
mesoderm) and their numbers remain
relatively constant throughout life.
Arranged in bundles surrounded by
connective tissue. striated (due to the
regular alternation of the contractile
proteins actin and myosin), with many
nuclei squeezed along the membranes (as
a result of the fusion of the many
myoblasts to form each long muscle fiber).
Muscle Tissue
Skeletal muscle cells (fibers), with crossstriations and peripheral nuclei.
Muscle Tissue
Higher power of skeletal muscle for details of cross-striations. Notice thin Z
discs and heavy A bands. From one Z disc to the next is a sarcomere, the
unit of muscle contraction. In the upper muscle cell notice shadowy
myofibrils running longitudinally.
Muscle Tissue
EM of several myofibrils running longitudinally
through skeletal muscle cell. Between
individual myofibrils lie the mitochondria (M)
and glycogen (G) of the cytoplasm. Within
each myofibril are the typical striations: A= A
band; I= I band; Z= Z line; and H= H band. The
banding is formed by the arrangement of
myosin and actin filaments.
Muscle Tissue
• Smooth muscle responsible for involuntary
movements in the internal organs. It forms
the contractile component of the digestive,
urinary, and reproductive systems as well
as the airways and arteries. Each cell is
spindle shaped with a single nucleus and
no visible striations
Muscle Tissue
Smooth muscle - long, slender central nuclei, lying within narrow,
fusiform cells that lie parallel to each other in a smooth arrangement.
(Muscle cells are often referred to as muscle fibers because of their
narrowness and length.)
Muscle Tissue
Smooth muscle - with cells more separated so as to see their extent and shape
better, and the central position of their nuclei. A loose, irregular connective
tissue (endomysium) lies between the cells. Nuclei seen in this c.t. belong to
fibroblasts mainly.
Muscle Tissue
Smooth muscle with wrinkled nuclei due to contraction of cells.
Muscle Tissue
EM of smooth muscle showing typical "hairy" look of primarily filaments in the
cytoplasm. Part of the cytoplasm is clear of filaments and shows mitochondria
and polyribosomes. The cell membrane is at the lower right of the field and shows
a few pinocytotic vesicles toward the extreme right. The left-hand extent of that
same membrane seems darker and denser: probably a plaque, where filaments
attach. The fuzzy density just outside the cell membrane is the basal lamina.
Muscle Tissue
• Cardiac muscle (contractile walls of the
heart), cardiomyocytes, also striated single
cells typically with a single centrally
located nucleus, contract on their own
intrinsic rhythms without any external
stimulation and attach to one another with
specialized cell junctions = intercalated
discs (both anchoring junctions and gap
junctions)  long, branching cardiac
muscle fibers that are, essentially, a
mechanical and electrochemical syncytium
with synchronized actions that pumps
blood under involuntary control.
Muscle Tissue
Cardiac muscle with cross-striations, dark intercalated discs, and centrally located
nuclei. Notice too that the nuclei are stubby in appearance, and that they lie in a
rather granular cytoplasm. Some of the intercalated discs form a straight line
across muscle fibers; others make a step-like arrangement.
Muscle Tissue
EM of intercalated disc between the ends
of two cardiac muscle cells. Both
desmosomes (1) and fasciae adheretes (2)
are identified. Notice mitochondria and
glycogen particles lying between
myofibrils.
Muscle Tissue
Another view of cardiac muscle showing wavy connective tissue (endomysium)
between muscle cells. Also, notice capillaries with r.b.c.'s; muscle is a highly
vascularized tissue. Some yellow granular cytoplasm can be seen inside the lower
muscle cells, where myofibrils are parted. This picture also gives some indication of
the branching of cardiac fibers.
Nervous Tissue
• excitable and capable of sending and receiving electrochemical signals that provide the
body with information.
• 2 main classes of cells: neuron (propagate information via electrochemical impulses,
called action potentials, which are biochemically linked to the release of chemical signals)
and neuroglia (play an essential role in supporting neurons and modulating their
information propagation)
Nervous Tissue
Neurons = distinctive morphology  role as
conducting cells, with 3 parts. The cell body includes
most of the cytoplasm, the organelles, and the
nucleus. Dendrites branch off the cell body and
appear as thin extensions. A long “tail,” the axon,
extends from the neuron body and can be wrapped in
an insulating layer known as myelin, which is formed
by accessory cells. The synapse is the gap between
nerve cells, or between a nerve cell and its target, for
example, a muscle or a gland, across which the
impulse is transmitted by chemical compounds known
as
neurotransmitters.
Neurons
categorized:
multipolar, bipolar and unipolar. When a neuron is
sufficiently stimulated, it generates an action
potential that propagates down the axon towards the
synapse. If enough neurotransmitters are released at
the synapse to stimulate the next neuron or target, a
response is generated.
Nervous Tissue
The second class of neural cells: neuroglia or glial cells, (from the Greek word for glue).
Astrocyte cells, (star shape) abundant in the CNS, have many functions: regulation of ion
concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters,
and formation of the blood-brain barrier. Microglia protect the nervous system against
infection (related to macrophages). Oligodendrocytes produce myelin in the CSN (brain and
spinal cord) while the Schwann cell produces myelin in the peripheral nervous system
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