Download The basement membrane anchors epithelium to the

The basement membrane anchors epithelium to the connective tissue
beneath it.
LEARNING OBJECTIVE [ edit ]
Describe the basement membranes and its diseases
KEY POINTS [ edit ]
The basement membrane is the fusion of two lamina, the basal lamina and the reticular lamina
(or lamina reticularis).
The lamina reticularis is attached to the basal lamina with anchoring fibrils (type
VII collagen fibers) and microfibrils (fibrillin).
The primary function of the basement membrane is to anchor down the epithelium to its
loose connective tissue underneath. This is achieved by cell-matrix adhesions through substrate
adhesion molecules (SAMs).
A group of diseases stemming from improper function of basement membrane zone are united
under the name epidermolysis bullosa.
Some diseases result from a poorly functioning basement membrane.
The cause can be genetic defects, injuries by the body's own immune system, or other
mechanisms.
The basement membrane is the fusion of two lamina, the basal lamina and the reticular lamina
(or lamina reticularis).
The primary function of the basement membrane is to anchor down the epithelium to its loose
connective tissue underneath. This is achieved by cell-matrix adhesions through substrate
adhesion molecules (SAMs).
Genetic defects in the collagen fibers of the basement membrane cause Alport syndrome.
Non-collagenous domain basement membrane collagen type IV is autoantigen (target antigen) of
autoantibodies in theautoimmune disease Goodpasture's syndrome.
A group of diseases stemming from improper function of basement membrane zone are united
under the name epidermolysis bullosa.
TERMS [ edit ]
basement membrane
Controls the traffic of cells and molecules between the dermis and epidermis, but also serves,
through the binding of a variety of cytokines and growth factors, as a reservoir for their controlled
release during physiological remodeling or repair processes.
collagen
any of more than 28 types of glycoprotein that forms elongated fibers, usually found in the
extracellular matrix of connective tissue.
connective tissue
A type of tissue found in animals whose main function is binding other tissue systems (such as
muscle to skin) or organs; it consists of the following three elements: cells, fibers, and a ground
substance (or extracellular matrix).
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Basement Membranes and
Diseases
The basement membrane is the fusion of
two lamina: the basal lamina and
the reticular lamina (or lamina
reticularis).
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The Basal Lamina
Basal lamina lining the outer surface of a cell membrane.
The lamina reticularis is attached to the basal lamina with anchoring fibrils (type VII collagen
fibers ) and microfibrils (fibrillin). The two layers are collectively known as the basement
membrane.
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and
connective tissues of vertebrates. It is the main component of connective tissue, and is the most
abundant protein in mammals.
The basal lamina layer can further be divided into two layers: the clear layer closer to the
epithelium is called the lamina lucida, and the dense layer closer to the connective tissue is
called the lamina densa. The electron-dense lamina densa membrane is about 30–70
nanometers in thickness, and consists of an underlying network of reticular collagen (type
IV) fibrils (fibroblast precursors) which average 30 nanometers in diameter and 0.1–2
micrometers in thickness. In addition to collagen, this supportive matrix contains intrinsic
macromolecular components.
The primary function of the basement membrane is to anchor down the epithelium to its
loose connective tissue underneath. This is achieved by cell-matrix adhesions through
substrate adhesion molecules (SAMs). The basement membrane also acts as a mechanical
barrier, preventing malignant cells from invading the deeper tissues. Early stages of
malignancy that are thus limited to the epithelial layer by the basement membrane are
called carcinoma in situ. The basement membrane is also essential
for angiogenesis (development of new blood vessels).
Basement membrane proteins have been found to acceleratedifferentiation of endothelial
cells. The most notable examples of basement membranes are in the glomerular filtration of
thekidney, by the fusion of the basal lamina from the endotheliumof
glomerular capillaries and the basal lamina of the epithelium of the Bowman's capsule; and
between lung alveoli and pulmonary capillaries, by the fusion of the basal lamina of the lung
alveoli and of the basal lamina of the lung capillaries, which is where oxygen and
CO2 diffusion happens.
DISEASES
Some diseases result from a poorly-functioning basement membrane. The cause can be
genetic defects, injuries by the body's own immune system, or other mechanisms.
Genetic defects in the collagen fibers of the basement membrane cause Alport syndrome or
hereditary nephritis, a genetic disorder characterized by glomerulonephritis, endstage kidney
disease, and hearing loss.
Goodpasture disease is the result of an autoimmune response directed at Collagen type IV
alpha-3-binding protein, resulting in damage to the lungs and kidneys, bleeding and kidney
failure.
A group of diseases stemming from improper function of basement membrane zones are
united under the nameepidermolysis bullosa (EB). This is an inherited connective tissue
disease causing blisters in the skin and mucosal membranes, with an incidence of 1/50,000.
Its severity ranges from mild to lethal. It is caused by a mutation in the integrinα6β4 celladhesion molecule on either the alpha or beta subunit.