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Embryology Integumentary System
Terms in this set (76)
What does integumentary consist of
Skin and Appendages Sweat Glands, Nails, Sebaceous Glands and Erector Muscles of the Hair
What are the functions of the skin?
The integument constitutes about 16% of the total body weight.
Its functions are:
Protect the body from injury, Protect against dehydration and
infection.It participates in sensory reception, excretion, thermoregulation, and maintenance of water balance.
What two primordial layers make up the skin?
It consists of two layers derived from surface ectoderm and its underlying mesenchyme.
From what primordial layer is the epidermis derived?
The epidermis is a superficial epithelial tissue that is derived
from surface ectoderm.
From what primordial layer is the dermis derived?
The dermis is a deeper layer composed of dense, irregularly
arranged connective tissue, derived from mesenchyme.
What is an embryo covered by?
Initially the embryo is covered by a single layer of ectodermal cells.
What is periderm?
This single layer divides in the beginning of the second month, and
a layer of flattened cells, the periderm or epitrichium, is laid down on the surface.
What happens to the cells of the periderm?
In the embryo, the cells of the periderm continually undergo keratinization and desquamation. The exfoliated peridermal cells form part of the vernix caseosa.
What are the different layers present in the skin?
What are melanocytes?
The melanocytes in the basal layer of the epidermis have processes that extend between the epidermal cells to supply the skin with melanin.
What is the primordium of the epidermis?
The primordium of the epidermis is a layer of surface ectodermal cells. These cells proliferate and form a layer of squamous epithelium, the periderm, and a basal (germinative) layer.
What happens to the cells of the periderm?
The cells of the periderm undergo keratinization and desquamation
continually and are replaced by cells arising from the basal layer.
What is verniz caseosa?
The vernix caseosa protects the developing skin from constant exposure to amniotic fluid, with its high urine
content during the fetal period.
Also the greasy vernix facilitates the birth of fetus.
What does the basal layer become?
The basal layer of the epidermis becomes the stratum germinativum, producing new cells that are displaced
into more superficial layers.
What are epidermal ridges?
Epidermal Ridges are proliferations of the stratum germinativum which extend into the developing dermis.The epidermal ridges produce grooves on the surface of the palms and soles,
including the fingers and toes. This constitutes the fingerprints.
In the late embryonic period where do neural crest cells what do they differentiate into?
Late in the embryonic period, neural crest cells migrate into the mesenchyme of the developing dermis and differentiate into
Where do melanoblasts migrate to and what do they differentiate into?
These cells migrate to the dermoepidermal junction and differentiate into melanocytes, forming melanin granules.
How do you increase the amount of melanin in skin?
Amount of melanin increases with exposure to ultraviolet rays.
What are Langerhans cells and what do they do?
Langerhans cells are derived from the bone marrow (mesoderm) and migrate into the epidermis. They are involved in antigen presentation.
What are merkel cells origin and what is their function?
Merkel cells are of uncertain origin. Probably function as mechanoreceptors.
Where can thick skin be found?
Thick skin covers the palms and soles; it has sweat glands but no
arrector muscles of the hair or sebaceous glands.
Where can thin skin be found?
Thin skin covers most of the rest of the body; it contains hair follicles, arrector muscles of hairs, sebaceous glands, and sweat glands.
When do mesenchymal cells start to produce collagenous and elastic connective tissue fibers?
11 week: Mesenchymal cells start to produce collagenous
and elastic connective tissue fibers.
How do sebaceous glands develop?
Sebaceous glands develop as buds from the sides of emerging
epithelial root sheaths of hair follicles. The glandular buds grow
into the surrounding connective tissue and branch to form the
primordia of several alveoli and their associated ducts.
What is sebum?
Sebum, is an oily secretion that is released into the hair follicle and
passes to the skin, helping to form the vernix caseosa.
Where are eccrine glands located?
Eccrine sweat glands are located in the skin throughout most of the body.
What are eccrine glands?
They are epidermal downgrowths (cellular buds) into the underlying mesenchyme. As the buds elongate their ends coil to form the primordium of the secretory part of the gland.
When do eccrine sweat glands begin to function?
Eccrine sweat glands begin to function shortly after birth.
Where are apocrine sweat glands found?
The distribution of the large apocrine sweat glands in humans is confined mostly to the axilla, pubic, and perineal regions and areolae of the nipples.
Where do the ducts of the apocrine gland open up?
The ducts of this glands open not onto the skin surface as do eccrine sweat glands, but unto the upper part of hair follicles.
When do the apocrine glands begin secretion?
They begin to secrete during puberty.
What is ichthyosis?
A skin disorders that results from excessive keratinization. Characterized by dryness of the skin and fishskin-like scaling. In severe cases a harlequin fetus may result.
What is a harlequin fetus?
Is a rare keratinizing disorder that is inherited as an autosomal
recessive trait. The skin is very thickened, ridged, and cracked.
Infants usually die on the first week of life. Incidence 1: 300,000 births.
What is the genotype of a colloid infant?
The Collodion infant is covered by a thick, taut membrane that resembles collodion or parchment. This membrane sheds completely after some weeks, occasionally leaving normal-appearing skin.
What is lamellar Ichthyosis?
Autosomal recessive disorder. The newborn appears to be a collodion baby, but the scaling persists. Growth of hair may be interrupted, and development of sweat glands is often stopped.
What is Congenital Ectodermal Dysplasia?
It is a very rare hereditary disorder, involves tissues that are ectodermal in origin. Teeth are completely or partially absent. Hairs, nails, and skin may be severely affected.
What is Ectrodactyl- ectodermal dysplasia - Clefting Syndrome?
Congenital skin condition inherited as an autosomal dominant trait. It involves both ectodermal and endodermal tissues, consisting of ectodermal dysplasia. Hypopigmentation of skin and hair, skanty hair and eyebrows, absence of eyelashes, nail dystrophy, hypodontia and microdontia, ectrodactyly (lobster-claw syndrome)
and cleft lip and palate.
What is the genotype of Ectrodactyl- ectodermal dysplasia - Clefting Syndrome?
Hypopigmentation of skin and hair, skanty hair and eyebrows, absence of eyelashes, nail dystrophy, hypodontia and microdontia, ectrodactyly (lobster-claw syndrome) and cleft lip and palate.
What is psoriasis?
Psoriasis is a skin disease characterized by excess cell proliferation in the stratum basale and in the stratum spinosum. This results in thickening of the epidermis and shorter regeneration time of the epidermis.
What areas are impacted by psoriasis?
Areas of friction: Elbows, knees, soles of feet
What is ehlers - danlos syndrome?
Ehlers-Danlos syndrome is an autosomal dominant genetic disorder involving the enzyme necessary for the hydroxylation of lysine residues of collagen. Characterized by extremely stretchable and fragile skin, hypermobile joints, aneurysms of blood vessels, and rupture of the bowel.
In ehler- danlos what type of collagen is affected?
It affects mainly Type I and Type III collagen.
What is Junctional epidermolysis bullosa?
JEB is a group of autosomal recessive disorders characterized by bulla (blister) formation. The cause is a mutation in the gene for laminin 5, which alters adhesion of stratum basale to the basement membrane. The epidermis is intact but is separated from the underlying dermis. Usually fatal by the time the child reaches 3 to 4 years of age due to hypoproteinemia, anemia, and infection.
What are angiomas?
Vascular anomalies in which some transitory and/or extra primitive
blood or lymphatic vessel persist.
What are Cystic lymphangiomas or cystic hygromas?
Cystic lymphangiomas or cystic hygromas: composed of
What is nevus flammeus?
Nevus flammeus, flat pink or red, flamelike blotch, often on the
posterior surface of the neck.
What is port - wine stain hemangioma?
Port-wine stain hemangioma is large and dark, nearly always
anterior or lateral on the face and/or neck.
What is Sturge - Weber syndrome, hemangioma?
Sturge - Weber syndrome, hemangioma in the area of distribution
of the trigeminal nerve, associated with angioma of the meninges of the brain.
What are cavernous angiomas?
Cavernous angiomas: composed of arteries and veins.
What is albinism?
It is an autosomal recessive trait where there is a lack of pigment in the skin, hairs, and retina; the retina usually shows some pigmentation. Melanocytes fail to produce melanin because of the lack of the enzyme tyrosinase.
What is absence of skin disorder?
Small areas of the skin fail to form, looking like ulcers. Most common in the scalp. Usually heals by scarring or a skin graft may be needed.
What is gynecomastia?
Development of the rudimentary lactiferous ducts in the male mammary tissue. During puberty about two thirds
of boys develop varying degrees of hyperplasia of the breasts.
Decreased level of testosterone is found in boys with gynecomastia.
What are supernumerary nipples?
Multiple nipples are also common in males, often mistaken for moles.
What is lanugo?
Lanugo, is the first hair that appears in the fetus, it is
soft, fine and lightly pigmented.
What is the association between lanugo and vernix caseosa?
Lanugo helps to hold the vernix caseosa on the natal period.
Alopecia totalis, is the loss of all head
hair. Is thought to be autoimmune.
What is alopecia?
Absence or loss of scalp hair may occur with other abnormalities of
the skin and its derivatives.
What is congenital alopecia (congenital universalis)?
Congenital alopecia may be caused by failure of hair follicles to
develop, or from follicles producing poor quality hairs.
what is alopecia areata?
Patch of baldness
What is alopecia totalis?
Alopecia totalis, is the loss of all head hair. Is thought to be autoimmune.
What is hypertrichosis?
Excessive hairiness results from the development of supernumerary hair follicles or from the persistence of lanugo hairs that normally disappear during the perinatal period.Localized hypertrichosis is normally associated with spina bifida occulta.
What is pili torti?
This is a familial disorder in which the hairs are twisted and bent.
Other ectodermal defects such as distorted nails may be associated with this condition.
What is Congenital Anonychia?
Absence of nails. It results from failure of nail fields to form or failure of the proximal nail folds to form nail plates. May be associated with abnormalities of the hair and teeth.
What primordial layers do teeth develop from?
Teeth develop from:
Neural crest cells
What is odontogenesis?
Odontogenesis is a continuous process involving reciprocal induction between neural crest mesenchyme and the overlying oral epithelium.
How many deciduous teeth are there typically
How many permanent teeth?
What are the 3 stages of tooth development?
Bud, Cap, and Bell
What do mesenchymal cells differentiate into.
The mesenchymal cells in the dental papilla differentiate into odontoblasts.`
What do odontoblasts produce?
which produce predentine, which later calcifies and becomes dentine, the second hardest tissue in the body.
What is enamel?
Enamel is the hardest tissue in the body. It overlies and protects the dentine from being fractured.
What produces enamel?
The enamel is produced by ameloblasts which differentiate from cells of the inner enamel epithelium.
What are natal teeth?
There are usually two teeth in the position of mandibular
incisors. Produce maternal discomfort during breast-feeding. The
infants tongue may be lacerated or the teeth may be aspirated.
Extraction of the teeth is advised. These children may need spacers to prevent overcrowding of the other teeth.
What is Amelogenesis Imperfecta?
Developmental aberration in enamel formation in the absence of systemic disorders. The enamel is hypoplastic, hypocalcified, or hypomature. There are 14 types of amelogenesis, depending on the type the enamel may be hard or soft, pitted or smooth, and thin or normal in thickness.
What is Dentinogenesis Imperfecta?
Common in white children. The teeth are brown to grey- blue with an opalescent sheen because the odontoblasts fail to differentiate
normally and poorly calcified dentine develops. Deciduous and permanent teeth are involved. Is an autosomal dominant disease.
How do tetracyclines affect teeth?
All tetracyclines are incorporated into the teeth, the critical period is from 14 week to 10th postnatal month. Tetracycline staining affects enamel and dentine because it binds to hydroxyapatite. Tetracyclines should not be given to pregnant woman or children younger than 8 years of age.
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