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A&P 3.2 Tissues
Transcript of A&P 3.2 Tissues
B. Nervous tissue is composed of two types of cells. (p. 136; Fig. 4.9)
1. Neurons are specialized cells that generate and conduct electrical impulses.
2. Supporting cells are nonconductive cells that support, insulate, and protect the neurons. Nervous Tissue Dense connective tissue is one of the two subclasses of connective tissue proper.
a. Dense regular connective tissue contains closely packed bundles of collagen fibers running in the same direction and makes up tendons and ligaments.
b. Dense irregular connective tissue contains thick bundles of collagen fibers arranged in an irregular fashion, and is found in the dermis.
4. Cartilage lacks nerve fibers and is avascular.
a. Hyaline cartilage is the most abundant cartilage, providing firm support with some pliability.
b. Elastic cartilage is found where strength and exceptional stretchability are needed, such as the external ear.
c. Fibrocartilage is found where strong support and the ability to withstand heavy pressure are required, such as the intervertebral discs.
5. Bone (osseous tissue) has an exceptional ability to support and protect body structures due to its hardness, which is determined by the additional collagen fibers and calcium salts found in the extracellular matrix.
6. Blood is classified as a connective tissue because it developed from mesenchyme, and consists of blood cells and plasma proteins surrounded by blood plasma. Stratified epithelia’s main function is protection.
a. Stratified squamous epithelium is composed of several layers with the cells on the free surface being squamous shaped and the underlying cells being cuboidal or columnar in shape.
b. Stratified cuboidal epithelium is rare, found mostly in the ducts of some of the larger glands.
c. Stratified columnar epithelium is found in limited distribution with small amounts in the pharynx, in the male urethra, and lining some glandular ducts.
d. Transitional epithelium forms the lining of the hollow organs of the urinary system that stretches as they fill. Simple epithelia are mostly concerned with absorption, secretion, and filtration.
a. Simple squamous epithelium is a single layer of fish scale–shaped cells.
b. Simple cuboidal epithelium is a single layer of cube-shaped cells forming the smallest ducts of glands and many kidney tubules.
c. Simple columnar epithelium is a single layer of column-shaped cells that line the digestive tract.
d. Pseudostratified columnar epithelium contains cells of varying heights giving the false impression of the presence of many layers. A. Embryonic and Fetal Development of Tissues 1. Primary germ layer formation is one of the first events of embryonic development.
a. Ectoderm is the most superficial of the layers.
b. Mesoderm is the middle layer.
c. Endoderm is the deepest layer.
2. The primary germ layers specialize to form the four primary tissues.
B. With increasing age, epithelia become thin, the amount of collagen fibers in the body decreases, and bone, muscle, and nervous tissue atrophy. Developmental Aspects of Tissues A. Tissue repair occurs in two ways: regeneration and fibrosis.
B. Three steps are involved in the tissue repair process.
1. Inflammation prepares the area for the repair process.
2. Organization restores the blood supply.
3. Regeneration and fibrosis effect permanent repair.
C. The generative capacity of tissues varies widely among the tissue types. Tissue Repair A. Cutaneous membrane, or skin, is an organ system consisting of a keratinized squamous epithelium firmly attached to a thick layer of dense irregular connective tissue.
B. Mucous membranes line body cavities that open to the exterior and contain either stratified squamous or simple columnar epithelia.
C. Serous membranes consist of simple squamous epithelium resting on a thin layer of loose connective (areolar) tissue. Covering and Lining Membranes A. Muscle tissues are highly cellular, well-vascularized tissues responsible for movement
B. There are three types of muscular tissue:
1. Skeletal muscle attaches to the skeleton and produces voluntary body movement.
2. Cardiac muscle is responsible for the involuntary movement of the heart.
3. Smooth muscle is found in the walls of the hollow organs. Muscle Tissue 1. Mesenchyme forms during the early weeks of embryonic development from the mesoderm layer and eventually differentiates into all other connective tissues.
2. Loose connective tissue is one of the two subclasses of connective tissue proper.
a. Areolar connective tissue serves to bind body parts together while allowing them to move freely over one another, wraps small blood vessels and nerves, surrounds glands, and forms the subcutaneous tissue.
b. Adipose (fat) tissue is a richly vascularized tissue that functions in nutrient storage, protection, and insulation.
c. Reticular connective tissue forms the internal framework of the lymph nodes, the spleen, and the bone marrow. Types of Connective Tissue 1. Ground substance is the unstructured material that fills the space between the cells and contains the fibers.
2. Fibers of the connective tissue provide support.
a. Collagen fibers are extremely strong and provide high tensile strength to the connective tissue.
b. Elastic fibers contain elastin, which allows them to be stretched and to recoil.
c. Reticular fibers are fine, collagenous fibers that form networks.
3. Each major class of connective tissue has a fundamental cell type that exists in immature and mature forms. Structural Elements of Connective Tissue 1. All connective tissue arises from an embryonic tissue called mesenchyme.
2. Connective tissue ranges from avascular to highly vascularized.
3. Connective tissue is composed mainly of nonliving extracellular matrix that separates the cells of the tissue. Common Characteristics of Connective Tissue Functions of Connective Tissue
1. The major functions of connective tissue are binding and support, protection, insulation, and transportation. Connective Tissue 1. Endocrine glands are ductless glands that secrete hormones by exocytosis directly into the blood or lymph.
2. Exocrine glands have ducts and secrete their product onto a surface or into body cavities.
a. Exocrine glands may be unicellular or multicellular.
b. Exocrine secretions in humans may be
merocrine, which are products released through exocytosis, or holocrine, which are synthesized products released when the cell ruptures. Glandular Epithelia Each epithelial tissue is given two names.
a. The first name indicates the number of layers present, either simple (one) or stratified (more than one).
b. The second name describes the shape of the cells. Classification of Epithelia 1. Composed of closely packed cells with little extracellular material between.
2. Adjacent epithelial cells are bound together by specialized contacts such as desmosomes and tight junctions.
3. Exhibits polarity by having an apical surface (free) and a basal surface (attached).
4. Supported by the underlying connective tissue.
5. Innervated but avascular.
6. Has a high regeneration capacity. Special Characteristics of Epithelium A. Features of Epithelia
1. An epithelium is a sheet of cells that covers a body surface or lines a cavity.
2. Epithelium occurs in the body as covering or lining epithelium, and as glandular epithelium. Epithelial Tissue A. Tissue specimens must be fixed (preserved) and sectioned (sliced) thinly enough to allow light transmission.
B. Tissue sections must be stained with dyes that bind to different parts of the cell in slightly different ways so that anatomical structures are distinguished from one another. I. Preparing Human Tissue for Microscopy Connective tissue: Supports, protects, binds
other tissues together
• Fat and other soft padding tissue Epithelial tissue: Forms boundaries between different
environments, protects, secretes, absorbs, filters
• Skin surface (epidermis)
• Lining of GI tract organs and other hollow organs Muscle tissue: Contracts to cause movement
• Muscles attached to bones (skeletal)
• Muscles of heart (cardiac)
• Muscles of walls of hollow organs (smooth) Nervous tissue: Internal communication
• Brain, spinal cord, and nerves Figure 4.1 Overview of four tissue types: epithelial, connective, muscle, and nervous tissues. (a) Classification based on number of cell layers. Basal surface Apical surface Basal surface Apical surface Simple Stratified Figure 4.2a Classification of epithelia. (b) Classification based on cell shape. Columnar Cuboidal Squamous Figure 4.2b Classification of epithelia. Nuclei of
cells Air sacs of
lung tissue Photomicrograph: Simple squamous epithelium
forming part of the alveolar (air sac) walls (125x). Location: Kidney glomeruli; air sacs
of lungs; lining of heart, blood
vessels, and lymphatic vessels; lining
of ventral body cavity (serosae). Function: Allows passage of
materials by diffusion and filtration
in sites where protection is not
important; secretes lubricating
substances in serosae. Description: Single layer of flattened
cells with disc-shaped central nuclei
and sparse cytoplasm; the simplest
of the epithelia. (a) Simple squamous epithelium Figure 4.3a Epithelial tissues. Simple
membrane Photomicrograph: Simple cuboidal
epithelium in kidney tubules (430x). Location: Kidney tubules;
ducts and secretory portions
of small glands; ovary surface. Function: Secretion and
absorption. Description: Single layer of
cubelike cells with large,
spherical central nuclei. (b) Simple cuboidal epithelium Figure 4.3b Epithelial tissues. Basement
cell Photomicrograph: Simple columnar epithelium
of the stomach mucosa (860X). Location: Nonciliated type lines most of
the digestive tract (stomach to anal canal),
gallbladder, and excretory ducts of some
glands; ciliated variety lines small
bronchi, uterine tubes, and some regions
of the uterus. Function: Absorption; secretion of
mucus, enzymes, and other substances;
ciliated type propels mucus (or
reproductive cells) by ciliary action. Description: Single layer of tall cells
with round to oval nuclei; some cells
bear cilia; layer may contain mucus-
secreting unicellular glands (goblet cells). (c) Simple columnar epithelium Figure 4.3c Epithelial tissues. Basement
layer Cilia Trachea Photomicrograph: Pseudostratified ciliated
columnar epithelium lining the human trachea (570x). 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. Function: Secretion, particularly of
mucus; propulsion of mucus by
ciliary action. 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. (d) Pseudostratified columnar epithelium Mucus of
mucous cell Figure 4.3d Epithelial tissues. Connective
membrane Nuclei Stratified
epithelium Photomicrograph: Stratified squamous epithelium
lining the esophagus (285x). Location: Nonkeratinized type forms
the moist linings of the esophagus,
mouth, and vagina; keratinized variety
forms the epidermis of the skin, a dry
membrane. Function: Protects underlying
tissues in areas subjected to abrasion. Description: Thick membrane
composed of several cell layers;
basal cells are cuboidal or columnar
and metabolically active; surface
cells are flattened (squamous); in the
keratinized type, the surface cells are
full of keratin and dead; basal cells
are active in mitosis and produce the
cells of the more superficial layers. (e) Stratified squamous epithelium Figure 4.3e Epithelial tissues. Transitional
membrane Photomicrograph: Transitional epithelium lining the urinary
bladder, relaxed state (360X); note the bulbous, or rounded,
appearance of the cells at the surface; these cells flatten and
become elongated when the bladder is filled with urine. Location: Lines the ureters, urinary
bladder, and part of the urethra. Function: Stretches readily and
permits distension of urinary organ
by contained urine. 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. (f) Transitional epithelium Figure 4.3f Epithelial tissues. Nucleus Rough ER Golgi
mucin Microvilli (a) (b) Figure 4.4 Goblet cell (unicellular exocrine gland). Simple duct structure
(duct does not branch) Secretory epithelium Duct Surface epithelium Alveolar
Salivary glands Compound
glands Simple branched
example in humans Simple
Mammary glands Compound alveolar Example
Duodenal glands of small intestine Compound tubular Example
glands Simple branched
Intestinal glands Simple tubular Compound duct structure
(duct branches) Figure 4.5 Types of multicellular exocrine glands. Simple duct structure (duct does not branch) Secretory
epithelium Duct Surface
Sebaceous (oil) glands Simple branched alveolar Example
example in humans Simple alveolar Example
Stomach (gastric) glands Simple branched tubular Example
Intestinal glands Simple tubular Figure 4.5 Types of multicellular exocrine glands (1 of 2). Secretory
epithelium Duct Surface
Salivary glands Compound
Mammary glands Compound alveolar Example
Duodenal glands of small intestine Compound tubular Compound duct structure (duct branches) Secretory
vesicles (a) Merocrine glands
secrete their products
by exocytosis. (b) In holocrine glands, the
entire secretory cell
secretions and dead
cell fragments. Secretory
cell fragments Figure 4.6 Chief modes of secretion in human exocrine glands. Collagen
propria Epithelium Photomicrograph: Areolar connective tissue, a
soft packaging tissue of the body (300x). Location: Widely distributed under
epithelia of body, e.g., forms lamina
propria of mucous membranes;
packages organs; surrounds
capillaries. Function: Wraps and cushions
organs; its macrophages phagocytize
bacteria; plays important role in
inflammation; holds and conveys
tissue fluid. Description: Gel-like matrix with all
three fiber types; cells: fibroblasts,
macrophages, mast cells, and some
white blood cells. (a) Connective tissue proper: loose connective tissue, areolar Figure 4.8a Connective tissues. Mammary
fat droplet Nucleus of
fat cell Photomicrograph: Adipose tissue from the
subcutaneous layer under the skin (350x). Location: Under skin in the
hypodermis; around kidneys and
eyeballs; within abdomen; in breasts. Function: Provides reserve food
fuel; insulates against heat loss;
supports and protects organs. Description: Matrix as in areolar,
but very sparse; closely packed
adipocytes, or fat cells, have
nucleus pushed to the side by large
fat droplet. (b) Connective tissue proper: loose connective tissue, adipose Figure 4.8b Connective tissues. Reticular
fibers White blood
(lymphocyte) Spleen Photomicrograph: Dark-staining network of reticular
connective tissue fibers forming the internal skeleton
of the spleen (350x). Location: Lymphoid organs (lymph
nodes, bone marrow, and spleen). Function: Fibers form a soft internal
skeleton (stroma) that supports other
cell types including white blood cells,
mast cells, and macrophages. Description: Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on the
network. (c) Connective tissue proper: loose connective tissue, reticular Figure 4.8c Connective tissues. Nuclei of
fibers Tendon Shoulder
joint Photomicrograph: Dense regular connective
tissue from a tendon (500x). Location: Tendons, most
ligaments, aponeuroses. Function: Attaches muscles to
bones or to muscles; attaches bones
to bones; withstands great tensile
stress when pulling force is applied
in one direction. Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast. (d) Connective tissue proper: dense connective tissue, dense regular Ligament Figure 4.8d Connective tissues. Fibrous
capsule Nuclei of
fibers Photomicrograph: Dense irregular
connective tissue from the dermis of the
skin (400x). Location: Fibrous capsules of
organs and of joints; dermis of
the skin; submucosa of
digestive tract. Function: Able to withstand
tension exerted in many
directions; provides structural
strength. Description: Primarily
irregularly arranged collagen
fibers; some elastic fibers;
major cell type is the fibroblast. (e) Connective tissue proper: dense connective tissue, dense irregular Figure 4.8e Connective tissues. Photomicrograph: Elastic connective tissue in
the wall of the aorta (250x). Heart Aorta Elastic fibers Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within the
walls of the bronchial tubes. Function: Allows recoil of tissue
following stretching; maintains
pulsatile flow of blood through
arteries; aids passive recoil of lungs
following inspiration. Description: Dense regular
connective tissue containing a high
proportion of elastic fibers. (f) Connective tissue proper: dense connective tissue, elastic Figure 4.8f Connective tissues. Matrix Chondrocyte
in lacuna Photomicrograph: Elastic cartilage from
the human ear pinna; forms the flexible
skeleton of the ear (800x). Location: Supports the external
ear (pinna); epiglottis. Function: Maintains the shape
of a structure while allowing
great flexibility. Description: Similar to hyaline
cartilage, but more elastic fibers
in matrix. (h) Cartilage: elastic Figure 4.8h Connective tissues. Collagen
in lacunae Intervertebral
discs Photomicrograph: Fibrocartilage of an
intervertebral disc (125x). Special staining
produced the blue color seen. Location: Intervertebral discs;
pubic symphysis; discs of knee
joint. Function: Tensile strength
with the ability to absorb
compressive shock. Description: Matrix similar to
but less firm than that in hyaline
cartilage; thick collagen fibers
predominate. (i) Cartilage: fibrocartilage Figure 4.8i Connective tissues. Central
canal Lamella Lacunae Photomicrograph: Cross-sectional view
of bone (125x). Location: Bones 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). Description: Hard, calcified
matrix containing many collagen
fibers; osteocytes lie in lacunae.
Very well vascularized. (j) Others: bone (osseous tissue) Figure 4.8j Connective tissues. Plasma Lymphocyte Red blood
cells Neutrophil 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. Location: Contained within
blood vessels. Function: Transport of
respiratory gases, nutrients,
wastes, and other substances. Description: Red and white
blood cells in a fluid matrix
(plasma). (k) Others: blood Figure 4.8k Connective tissues. Matrix Chondrocyte
in lacuna Costal
cartilages Photomicrograph: Hyaline cartilage from the
trachea (750x). 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. Function: Supports and reinforces;
has resilient cushioning properties;
resists compressive stress. Description: Amorphous but firm
matrix; collagen fibers form an
imperceptible network; chondroblasts
produce the matrix and when mature
(chondrocytes) lie in lacunae. (g) Cartilage: hyaline Figure 4.8g Connective tissues. Nervous tissue Neuron
processes Cell body
of a neuron Nuclei of
cells Axon Cell body Neuron processes Dendrites 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 nonirritable supporting cells
(not illustrated). Location: Brain, spinal
cord, and nerves. Function: Transmit electrical
signals from sensory receptors
and to effectors (muscles and
glands) which control their activity. Photomicrograph: Neurons (350x) Figure 4.9 Nervous tissue. Part of
fiber (cell) Striations Nuclei Photomicrograph: Skeletal muscle (approx. 460x).
Notice the obvious banding pattern and the
fact that these large cells are multinucleate. Location: In skeletal muscles
attached to bones or
occasionally to skin. Function: Voluntary movement;
locomotion; manipulation of the
environment; facial expression;
voluntary control. Description: Long, cylindrical,
multinucleate cells; obvious
striations. (a) Skeletal muscle Figure 4.10a Muscle tissues. Nucleus Striations Intercalated
discs Photomicrograph: Cardiac muscle (500X);
notice the striations, branching of cells, and
the intercalated discs. Location: The walls of the
heart. Function: As it contracts, it
propels blood into the
circulation; involuntary control. Description: Branching,
striated, generally uninucleate
cells that interdigitate at
(intercalated discs). (b) Cardiac muscle Figure 4.10b Muscle tissues. Figure 4.10c Muscle tissues. Nuclei Smooth
cell Photomicrograph: Sheet of smooth muscle (200x). Location: Mostly in the walls
of hollow organs. Function: Propels substances
or objects (foodstuffs, urine,
a baby) along internal passage-
ways; involuntary control. Description: Spindle-shaped
cells with central nuclei; no
striations; cells arranged
closely to form sheets. (c) Smooth muscle Visceral pleura Parietal pleura Visceral
peritoneum (c) Serous membranes line body cavities
closed to the exterior. (b) Mucous membranes line body
cavities open to the exterior. (a) Cutaneous membrane (the
skin) covers the body surface. Visceral pericardium Parietal pericardium Esophagus lining Mucosa of mouth Mucosa of lung
bronchi Mucosa of nasal
cavity Cutaneous membrane
(skin Figure 4.11 Classes of membranes. Artery Migrating white
blood cell Inflammation sets the stage:
• Severed blood vessels bleed and inflammatory chemicals are
• Local blood vessels become more permeable, allowing white
blood cells, fluid, clotting proteins and other plasma proteins
to seep into the injured area.
• Clotting occurs; surface dries and forms a scab. Inflammatory
chemicals Vein Epidermis Blood clot in
incised wound Scab 1 Figure 4.12 Tissue repair of a nonextensive skin wound: regeneration and fibrosis (1 of 3). Organization restores the blood supply:
• The clot is replaced by granulation tissue, which restores
the vascular supply.
• Fibroblasts produce collagen fibers that bridge the gap.
• Macrophages phagocytize cell debris.
• Surface epithelial cells multiply and migrate over the
granulation tissue. Macrophage Fibroblast Area of granulation
tissue ingrowth Regenerating
epithelium 2 Figure 4.12 Tissue repair of a nonextensive skin wound: regeneration and fibrosis (2 of 3). Fibrosed
area Regeneration and fibrosis effect permanent repair:
• The fibrosed area matures and contracts; the epithelium
• A fully regenerated epithelium with an underlying area of
scar tissue results. Regenerated
epithelium 3 Figure 4.12 Tissue repair of a nonextensive skin wound: regeneration and fibrosis (3 of 3). Ectoderm Muscle and connective
tissue (mostly from
mesoderm) Nervous tissue
(from ectoderm) Epithelium 16-day-old embryo
(dorsal surface view) Endoderm Mesoderm Figure 4.13 Embryonic germ layers and the primary tissue types they produce.