Chapter 4: The Tissue Level 10/16/2013
Tissue Types: Simple outline
Connective tissue proper
Nervous Tissue Types: There are 4 types of tissues in the body – epithelial, connective, muscular, and nervous
Epithelial tissue: all epithelial tissue has a basement membrane, which is a selective membrane
that regulates substances differing from the underlying connective tissues and supports the epithelial
tissue. The bottom layer of the basement membrane is dense connective tissue, which is highly
vascularized connective tissue. There are 2 divisions of epithelial tissue: glandular (nonmembranous) and
Glandular epithelial tissue: classified by mode of secretion
Endocrine glands: ductless glands that release hormones directly into the extracellular fluid (interstitial
fluid and blood plasma)
Exocrine glands: either unicellular or multicellular
Unicellular exocrine glands: not equipped with ducts
The only type of unicellular exocrine glands in the human body is the goblet cell, and they are dispersed in
simple ciliated columnar epithelial tissue, and ciliated pseudostratified columnar epithelial tissue.
Multicellular exocrine glands: all are equipped with ducts; consist of duct systems (simple or
compound) and a secretory portion (tubular)
Functional classification: mode of secretion used by the secretory portion of the multicellular exocrine
glands to release their products
Apocrine: apex of the secretory cells pinch off to release accumulated products (no examples in the
In apocrine sweat glands, “apocrine” is a misnomer because the apocrine sweat glands use the merocrine
mode of secretion
Merocrine: the secretory cell undergoes exocytosis to release products
Holocrine: the secretory cell ruptures to release its accumulated products
Membranous epithelial tissue: there are 3 types of epithelial cells based on shape: squamous,
cuboidal, and columnar. Membranous epithelial cells are sheetlike (like a membrane).
Simple membranous epithelial tissue: consists of a single layer of cells
Simple squamous: forms part of the filtration membrane in the kidneys, part of the respiratory
membrane in the lungs (involved in the diffusion of gases), and lines the structures in the circulatory system
Endothelium: simple squamous epithelial tissue that lines the structures in the circulatory system
Mesothelium: simple squamous epithelial tissue that forms part of the serous membrane
The endothelium and mesothelium provide a frictionless surface for the movement of substances
Simple cuboidal: involved in secretion and absorption. It is located in the germinal epithelium,
which is the outer covering in the ovary composed of simple cuboidal epithelial tissue.
Simple columnar: can either be ciliated or nonciliated; columnar cells contain goblet cells, which
secrete mucus Ciliated simple columnar: cilia beat to create a unidirectional current that propels mucus, and lines
the fallopian (uterine) tubes, where cilia beat to create a unidirectional current that moves ova (eggs) or
zygotes (fertilized eggs)
Location: lines parts of the respiratory system, such as the bronchi (tubelike structures that branch from
the trachea and into the lungs)
Function: secretion of mucus, propulsion of mucus by ciliary action
Nonciliated simple columnar: cilia are absent, but microvilli might be present
Location: lines most of the GI tract, the lining of the small intestine (where it expresses microvilli, which
increases the surface area for absorption)
Function: absorption and secretion of the digestive enzymes
Simple pseudostratified columnar: a simple layer of cells of different heights, so their nuclei also
appear to be at different heights, giving false (“pseudo”) implication of stratification. Can either be ciliated or
Ciliated simple pseudostratified columnar: columnar cells are endowed with goblet cells
(referred to as the respiratory epithelium)
Location: lines most of the structures in the respiratory system
Nonciliated simple pseudostratified columnar: lines the ducts in the male reproductive
system, where it confers some level of protection
Location: spermcarrying ducts in the male (epididymis, vas deferens, ejaculatory duct, and urethra)
Stratified membranous epithelial tissue: several layers of cells
Stratified squamous: apical cells are flattened; can either be keratinized or nonkeratinized
Keratinized stratified squamous: apical cells are impregnated with a tough fibrous protein called
keratin, hence, this tissue is abrasive and resistant
Location: the epidermis of the skin
Function: protection against trauma and infection
Nonkeratinized stratified squamous: confers protection to the structure it lines
Location: in the tracts of the body (tract: a body system with an opening to the exterior)
GI tract: 2 openings
Urinary tract: 1 opening
Reproductive tract: 1 opening Respiratory tract: 1 opening
Entry points of these tracts are lined by this type of
Transitional epithelial tissue: 6 layers of comeshaped (cuboidal) apical cells, 3 layers of flattened
Cuboidal cells come when urinecontaining structures are empty, flattened apical cells come with full
Connective tissue: all connective tissue is derived from the mesenchyme (the embryonic
connective tissue, which is derived from the embryonic germ layer called the mesoderm). 4 types of
cells are derived from the mesenchyme, and each type gives rise to a class of connective cell tissue – they
are fibroblasts, Chondroblasts, osteoblasts, and hematopoietic stem cells.
All connective tissue is composed of 2 parts: the living portion and the nonliving portion. The living portion
includes the 4 cell types from the mesenchyme. The nonliving portion, where connective tissue cells are
dispersed, is called the extracellular matrix, which consists of the ground substance and the fibers.
The ground substance is composed of interstitial fluid and has cell adhesion molecules that attach
connective tissue cells to the matrix. It also includes proteoglycans composed of protein cores with
glycosaminoglycan (GaGs) attached. Generally, a high level of GaGs means a higher stiffness of
Connective tissue proper: fibroblasts (first type of cell derived from the mesenchyme) secrete
the cell tissue class connective tissue proper. The matured fibroblasts are called fibrocytes, which reside
in the connective tissue proper. The consistency of the ground substance/matrix is gellike. Based on fiber
content, there are 2 types/subclasses of connective tissue proper – loose and dense (fibrous)
Loose connective tissue proper: areolar, adipose, and reticular
Areolar connective tissue proper: the most abundant and widely distributed type of connective
tissue in the body. It is highly vascularized, hence, it supports epithelial membranes of the body and is
therefore referred to as the “packing material” of the body
Adipose connective tissue proper: composed of cells called adipocytes (fat calls), which
store (and expand in order to store large amounts of) pure triglycerides (fat).
Location: the hypodermis, surrounding vital organs, and in the ventral body cavity
Acts as an insulator to prevent and minimize heat loss from the body
Storage of triglycerides, which are the most concentrated and efficient form of stored energy in the
Cushions vital organs Holds vital organs in their correct anatomical positions
Reticular connective tissue proper: highly branched cells that form networks inside organs called
the stroma. Stroma inside lymphoid organs (lymph nodes, spleen, thymus) provide support for the
proliferation of the new cells (lymphoid cells), which go on to become macrophages, Tcells, and Bcells.
Hence, reticular connective tissue proper is associated with the immune system.
Dense (fibrous) connective tissue proper: regular or irregular; dense connective tissue is highly
fibrous; it consists of high amounts of collagen in bundles. Hence, dense connective tissue is referred to as
fibrous connective tissue.
Dense regular connective tissue proper: bundles of collagen arranged in “regular” fashion,
meaning all the collagen bundles face the same direction and therefore can resist pressure, tension, force,
and stress applied in one direction against the direction in which the collagen bundles are facing. Dense
regular tissue is poorly vascularized.
Location: tendons (which connect skeletal muscle to bone), Aponeruoses (sheetlike tendons that
connect skeletal muscle to skeletal muscle; ex. the galea aponeurotica, which connects the frontalis and the
occipitalis), and ligaments (cordlike structures that bind bones at joints).
Function: with the bundles of collagen facing one direction, dense regular tissue can resist pressure,
tension, stress, and force applied in only one direction.
Dense irregular connective tissue proper: bundles of collagen fibers arranged in an irregular
fashion, meaning bundles face in all directions to resist pressure, tension, force, and stress applied from
several directions. Dense irregular tissue is highly vascularized (like areolar connective tissue), hence, it is
located around avascular tissue (such as epithelial tissue or cartilage).
Location: reticular layer of the dermis; forms a capsule around avascular/poorly vascularized structures
(perichondrium: surrounding cartilage, periosteum: surrounding bone)
Cartilage: Chondroblasts (2 type of cell derived from mesenchyme) secrete the cell tissue class
cartilage. Matured Chondroblasts are called chondrocytes, which reside in the cartilage (living portion).
The nonliving portion, the ECM, has a semisolid consistency because of the level of GaGs. Shallow
cavities called lacunae form in the ECM, and chondrocytes reside in the lacunae. Hence, cartilage is
surrounded by perichondrium composed of dense irregular connective tissue. Cartilage has 3 types: hyaline
cartilage, elastic cartilage, and fibrocartilage.
Hyaline cartilage: embryonic skeleton is composed mainly of hyaline cartilage. After a process called
ossification (osteogenesis), most of the hyaline cartilage is converted into bone tissue. After
ossification, hyaline cartilage persists as articular cartilage.
Articular cartilage: a thin layer of hyaline cartilage that caps the end of the epiphysis and persists as
the epiphyseal plate, which is located at the junction of the diaphysis with an epiphysis.
Costal cartilage: connects the ribcage to the sternum
Functions Cushioning (articular cartilage)
Reinforcement (costal cartilage; hyaline cartilage in the trachea and the larynx)
Lengthening of long bones (epiphyseal plates)
Elastic cartilage: similar to dense connective tissue and hyaline cartilage, but has more elastic fibers,
which have the stretchrecoil properties. Elastic fibers stretch to accommodate pressure, and recoil to
assume the original size and length when pressure is removed.
Ligament flava in between the lateral aspects of adjacent vertebrae
The epiglottis – a flaplike structure that closes off the glottis (the opening into the larynx) when
swallowing to prevent swallowed substances from getting back up
Pinna of the external ear – flaplike pinna directs sound waves into the external auditory canal for the
process of hearing
Function: elastic cartilage allows for stretching under pressure and recoiling when pressure is removed
Fibrocartilage: a blend between dense regular tissue and hyaline cartilage
Location: forms invertebral discs, the pubic symphysis, and the menisci (pads of fibrocartilage in synovial
joints that minimize wear and tear of the joint)
Function: exhibits strength with flexibility and acts as a shock absorber
Bone: osteoblasts (3 type of cell type from the mesenchyme) secrete the cell tissue class
osseous/bone tissue. Matured osteoblasts are called osteocytes and reside in bone tissue (living
portion). The nonliving portion, the ECM, is completely solid based on the high amount of GaGs present.
Osseous/bone tissue is composed of both organic and inorganic material. The organic component is the
osteoid, which is secreted by the osteoblasts and is made up of collagen fibers. The inorganic
component, called the inorganic matrix, is called the hydroxyl apatite (calcium phosphate salts), which
are calcium crystals that are incorporated into the matrix of bone tissue to solidify the bone’s ECM.
Collagen fibers and the hydroxyl apatite perform solidification of the matrix of bone tissue.
Functions: support and protection, movement, calcium storage, and production of red blood cells (in bones
that store red bone marrow)
Hematopoietic stem cells are located in the red bone marrow, stored in certain bones
Blood: hematopoietic stem cells (4 type of cell derived from the mesenchyme) secrete the blood
cells in blood. White blood cells are leukocytes. Red blood cells are erythrocytes. The source for the
hematopoietic stem cells is red bone marrow, which is also known as myeloid tissue. Blood is secreted
by the myeloid tissue.
Blood consists of the fluid matrix (plasma) and the formed elements – white blood cells, red blood cells, and
platelets. Muscle tissue: skeletal, cardiac, and smooth; all muscle tissue is organized with connective tissue,
blood vessels, and nerves to form a muscle (which is an organ). So, when you look at the function, you look
at muscles as organs.
Skeletal muscle tissue: composed of striated, multinucleated, long, cylindrical cells called fibers;
controls voluntary movement
Cardiac muscle tissue: striated, uninucleate, highly branched cells that form intercalated discs
(with desmosomes and gap junctions); controls involuntary movement
Smooth muscle tissue: nonstriated, uninucleate, spindleshaped cells that control involuntary
Nervous tissue: composed of 2 cell types – neurons (nerve cells that act as conducting cells) and
neuroglia (supporting cells that are nonconductors)
Neurons have 3 parts: the cell body (biosynthetic center), dendrites (receptive regions), and the axon
Cell body: (called soma or perikaryon) contains a prominent nucleus and a prominent nucleoli, which is
indicative of high rates of protein synthesis. Hence, the cell body of a neuron is referred to as the
biosynthetic center. Cell bodies lack centrosomes, which means they lack centrioles, which means
that neurons are amitotic.
Dendrites: extending from the cell body, dendrites are tapered; a neuron can have several dendrites (at
least one) and act to receive electrical signals or chemical signals coming to the neuron (hence, the
dendrites are referred to as the receptive regions of the neuron)
Axon: only 1 per neuron; the axon generates and transmits action potentials, electrical signals that
are selfpropagating and do not decrease in intensity over distance. They are uniform in diameter, and can
be myelinated (only part of the neuron that can be myelinated). Even though each neuron can only have
one axon, the axon branches profusely at the end to form end branches called telodentria – knoblike
structures called axon terminals (boutons, synaptic knobs), which contain vesicles that contain
Neurotransmitters: chemical mediators used by neurons for communication
Axon terminals release neurotransmitters when the neuron is excited, hence the axon terminals are referred
to as the secretory regions of the neuron. Chapter 5: The Integumentary System 10/16/2013
Membranes act as simple organs. An organ is composed of at least 2 tissue types, 1 always being
epithelial tissue. Membranous epithelia are always supported by connective tissue. The simplest type of
organ in the human body is the membrane, which is a sheetlike structure that is composed of at least 2
types of tissues. There are 3 types of membranes in the body – cutaneous, mucous, serous, and synovial,
3 of which are epithelial membranes.
Cutaneous membrane: also known as the skin; the largest organ of the body and is composed of 3
layers – the overlaying keratinized stratified squamous epithelia, the underlying areolar connective tissue
(papillary layer), and the immediately deep dense irregular connective tissue layer (the reticular layer)
Mucous membrane: lines structures of the body’s tracts; composed of 2 layers – overlying tissue is
nonkeratinized stratified squamous epithelial OR simple columnar epithelial tissue, underlying tissue is
alveolar connective tissue, which is referred to as the lamina propria in this specific location.
Serous membrane: consists of 2 layers – the outer parietal layer and the inner visceral
layer. In each layer, the overlying tissue is simple squamous epithelial tissue (called the mesothelium)
and the underlying tissue is areolar connective tissue.
Synovial membrane: the only connective tissue membrane (the rest are epithelial); found in joints.
The overlying issue is dense irregular connective tissue and the underlying tissue is areolar connective
The integumentary system: the integumentary system has 2 divisions – the skin and the accessory
The skin: (cutaneous membrane) the skin is the largest organ of the body and is composed of the
superficial epidermis and the deep dermis. There are 2 types of skin, classified by thickness – thick skin
and thin skin.
The superficial epidermis: in thin skin, the superficial epidermis is composed of 4 layers of strata.
In the thick skin, the epidermis is composed of 5 layers of strata.
Thin skin: found all over the body, except for in the palms and soles; has 4 layers (the lucidum is absent)
Stratum basale: deepest stratum, supported by the basement membrane. It is a single layer of
cuboidal cells, including keratinocytes, melanocytes, and merkel cells
Keratinocytes: the most abundant type of cell in the stratum basale. These cells undergo mitosis
rapidly to provide the other layers with new cells (they push the new cells up) hence, the stratum basale is
also known as the stratum germitavium.
Melanocytes: these cells produce melanin contained in granules called melanosomes. Since UV
radiation can alter DNA replication to cause cancer of the keratinocytes, melanosomes release onto the
superficial face of the keratinocytes, protecting them via melanin from UV radiati