BIOL 2010 Lecture Notes - Lecture 6: Lanugo, Signify, Desmosome

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Published on 22 Feb 2017
School
TNTECH
Department
Biology
Course
BIOL 2010
Professor
Chapter 6 Integumentary System
The Integumentary System
o Made up of the integument (skin) and the accessory organs (hair, nails, cutaneous
glands)
o It is the most noticeable organ system
It is also the one that shows signs of aging first
Can show symptoms from various diseases of other organ systems as well
Jaundice and the liver for example
o Dermatology is the study of integument
Skin
o Largest and heaviest organ of the body
o Made of two parts:
Epidermis
Dermis
o The hypodermis is not part of the skin but is usually discussed here
Indistinct boundary between dermis and hypodermis
Made of areolar tissue and adipose tissue
Regions with predominately adipose tissue is called subcutaneous
fat
o Not uniformly distributed on an individual or between
sexes
o Skin Thickness
Most regions are 1-2 mm in thickness
Ranges though from 0.5 mm for eyelids to 6 mm on the shoulder
Skin is classified as thick or thin based on the thickness of the epidermis
alone
Thick skin found of palms, soles, and corresponding surfaces on
fingers and toes
o Epidermis alone is 0.5 mm
Has thicker stratum corneum than thin skin
o Lacks hair follicles and sebaceous glands but has sweat
glands
Thin skin covers the rest of the body
o Average thickness of epidermis is 0.1 mm
o Contains hair follicles, sweat, and sebaceous glands
o Functions of the Skin
Contains the body
Resists trauma and infection
Thanks to keratin, abundant desmosomes, being fairly dry, and
slightly acidic (pH of 4-6, the so called “acid mantle”)
Serves as a barrier for:
Water loss or excessive water gain
Barrier to UV radiation
Barrier for certain chemicals
Vitamin D synthesis
Sensation
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Not uniform in distribution:
o More abundant in face, palms, fingers, soles, nipples, and
genitalia
Multiple sensations originate from the receptors in the skin:
o Hot, cold, touch, texture, pressure, vibration, pain
Thermoregulation
Via cutaneous vasoconstriction and vasodilation
Nonverbal communication
A Closer Look at the Epidermis
o Keratinized, squamous epithelium
o Lacks blood vessels
Relies on diffusion of nutrients from underlying connective tissue
o Some nerve endings for touch and pain
o Several different cell types present:
Stem cells undifferentiated cells that give rise to keratinocytes in the
stratum basal
Keratinocytes major cell; responsible for making keratin
Melanocytes responsible for making melanin; cells remain in the stratum
basal
Packages of melanin (melanosomes) are exocytosed and absorbed
by nearby keratinocytes
Keratin protects the nucleus of the keratinocyte from UV radiation
Tactile cells involved in sensation of touch; tactile discs include the cell
and associated nerve fiber
Dendritic cells immune cells that have migrated to the stratum spinosum
or stratum granulosum
o Layers of the Epidermis
From deep to superficial
Stratum basal
Stratum spinosum
o Spines are an artifact of histological slide preparation
Stratum granulosum
o Keratohyalin granules present
Stratum lucidum
o Only in thick skin
o Stratum corneum
Made of dead cells
Life History of Keratinocytes
o Whole process takes 30-40 days
o Begins in stratum basal with differentiation from stem cells
Process can be sped up/increased by constant abrasion leading to
production of a thicker epidermis (callus or corn)
o Pushed towards the surface by further division of cells
Cells of the stratum spinosum are rarely seen dividing; instead they begin
to accumulate pre-keratin molecules
o In stratum granulosum, the following beings to occur:
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Document Summary

The integumentary system: made up of the integument (skin) and the accessory organs (hair, nails, cutaneous glands, it is the most noticeable organ system. It is also the one that shows signs of aging first. Can show symptoms from various diseases of other organ systems as well. Jaundice and the liver for example: dermatology is the study of integument. Skin: largest and heaviest organ of the body, made of two parts: Dermis: the hypodermis is not part of the skin but is usually discussed here. Made of areolar tissue and adipose tissue. Regions with predominately adipose tissue is called subcutaneous fat: not uniformly distributed on an individual or between, skin thickness. Most regions are 1-2 mm in thickness sexes. Ranges though from 0. 5 mm for eyelids to 6 mm on the shoulder. Skin is classified as thick or thin based on the thickness of the epidermis alone.

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