Anatomy II - Module 1- Student- Integumentary System-2021_075431.pdf

Anatomy of the integumentary systems

1. ANATOMY II-NURSING& MIDWIFERY
MR. BRIGHT OWUSU
Department of Nursing and Midwifery
Faculty of Health and Allied Sciences (FHAS)
Pentecost University College
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2. COURSE CODE: NURS 102 / MWF 102
COURSE DESCRIPTION:
This course is designed to help you (student) understand the normal structure
of the human body and apply the knowledge acquired when caring for
patients.
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COURSE OBJECTIVES
By the end of the course, you (student) will be able to:
1.Describe the integumentary system –skin and its appendages
2.Describe the organs of the musculoskeletal system;
3.Describe the organs of the central and peripheral nervous systems
4.Describe the organs of the endocrine system;
5.Describe the structure of the organs of the genito-urinary system;
6.Describe the organs of the male and female reproductive systems;
❑State the relations, blood supply, lymphatic drainage, nerve supply of the organs
described.
❑Apply the knowledge in other fields of study e.g. pathology/physiology and nursing
procedures such as administration of drugs, catheterization, obstetrics and gynaecology.

3. COURSE CONTENT
TOPICS (UNITS):
1.Integumentary System
2.Musculoskeletal System
3.Central and Peripheral Nervous System
4.Endocrine System
5.Genito-urinary System
6.Special Sensory Organs
7.Reproductive System
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4. UNIT ONE: INTEGUMENTARY SYSTEM
TOPICS:
1.Introduction
2.The Skin as an Organ
3.Structure of the Skin and Subcutaneous
Tissue
4.Functions of the Skin
5.Epidermal Derivatives: Hair and Nails
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SECTION1: INTRODUCTION
The integumentary system is the set of organs forming
the outermost layer of an animal's body.
Structurally, the integumentary system consists of the skin
and its derivatives(hair, nails, andcutaneous glands).
Functionally, the integumentary system acts as a physical barrier between the
external environmentand the internal environmentthat it serves to protectand
maintain.
it may serve to maintain water balance,
protect the deeper tissues,
excrete wastes,
regulate body temperature,
is the attachment site for sensory receptors to detect pain, sensation, pressure,
and temperature
Vitamin D production

6. Introduction cont.
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Dermatologyis the scientific study and medical treatment of the integumentary
system.
The integumentary system is the most easily examined of the organ systems
―its appearance provides important clues not only to its own health but also to
deeper disorders such as liver cancer, anemia, and heart failure.
―it is also the most vulnerable organ system,
▪exposed to radiation, trauma, infection, and injurious chemicals.
Consequently, it needs and receives more medical attention than any other organ
system.
―inspection of the skin, hair, and nails is significant part of a physical exam

7. SECTION2: THE SKIN AS AN ORGAN
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NOBRANCHOFSCIENCEHITSASCLOSETOHOMEASTHESCIENCEOFOUROWN
BODIES
❑Chapter Objectives:
By the end of this section, you will be able to:
Explain why the skin is considered an organ and a component of the
integumentary system.

8. THE SKIN AS AN ORGAN
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The skin is an organ, because it consists of
several kinds of tissues that are structurally
arranged to function together.
The skin is the largestand heaviestorgan of
the body,
―covers over 7,600 sq cm (3,000 sq in.) in
the average adult,
―accounts for approximately 7% of a
person’s body weight Figure: Structure of the skin with its tissues

9. SECTION3: STRUCTURE OFTHESKINAND
SUBCUTANEOUS TISSUE
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NOBRANCHOFSCIENCEHITSASCLOSETOHOMEASTHESCIENCEOFOUROWNBODIES
❑Chapter Objectives:
By the end of this section, you will be able to:
Describe the histological structure of the epidermis, dermis, and
subcutaneous tissue; and
Discuss the skin’s color and markings.
Summarize the transitional events that occur within each of the epidermal
layers.

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The skin is a dynamic interface between
the bodyand the external environment.
―Hence, protectsthe body from the
environment even as it allows for
communicationwith the
environment.
The skin, or integument and its
accessory structuresconstitute the
integumentary system.
―accessory structures include; hair,
glands, andnails
―also included in the integumentary
system are the millions of sensory
receptors of the skin and its
extensive vascular network.
STRUCTURE OF THE SKIN

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The skin consists of two
principal layers:
1.Epidermis–stratified
squamous epithelium
2.Dermis–a deeper
connective tissue layer
Below the skin is another
connective tissue layer, the
hypodermis
(subcutaneous tissue)
―The hypodermis
connects the skin to
underlying organs.
―Not part of skin
Layers of the Skin

12. Thickness of the Skin
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The skin is of variable thickness, averaging
1.5 mm.
―most of the skin is 1 to2 mm thick
―however, the skin ranges from less than
0.5 mm on the eyelids to 6 mm between
the shoulder blades.
This difference is due mainly to variation
in the thickness of the dermis.
However, skin is classified as thickor thin
skin
―based on the relative thickness of the
epidermis alone,
―especially the surface layer of dead cells
called the stratum corneum.

13. Thickness of the Skin cont.
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❑Thin skin: epidermis has a thin stratum
corneum
―covers the rest of the body
―is thinnest on the eyelids, external
genitalia, and tympanic membrane
(eardrum),
▪here it is approximately 0.5 mm thick
―possesses hair follicles, sebaceous glands
and sweat glands
❑Thick skin: epidermishasa very thick,
tough stratum corneum
―covers the parts of the body exposed to
wear andabrasion,
―such as the soles of the feet and palms of the hand, and corresponding surfaces on
fingers and toes
▪in these areas, it is about 6 mm thick.
―has sweat glands, but no hair follicles or sebaceous (oil) glands

14. THE EPIDERMIS
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The epidermisis the superficial protective layer of the skin.
―its derived from ectoderm,
―its composed of keratinized stratified squamous epithelium that varies in
thickness
▪that is, all (surface) but the deepest layers are composed of dead cells packed
with the tough protein keratin.
Like other epithelia, the epidermis;
―lacks blood vessels and
―depends on the diffusion of nutrients from the underlying connective tissue.
It has sparse nerve endings for touch and pain,
―but most sensations of the skin are due to nerve endings in the dermis.

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The epidermis usually consists of four zones (five in
thick skin; palms and soles) described here in order
from deep to superficial.
1.Stratum Basale (basal layer):
―Keratinocytes, Melanocytes, Tactile (Merkel) cells
2.Stratum Spinosum (spiny layer):
―consists of keratinocytes and dendritic
(Langerhans) cells
3.Stratum Granulosum (granular layer):
―dendritic (Langerhans) cells
4.Stratum Lucidum (clear layer):
―Keratinocytes
5.Stratum Corneum (hornlike layer):
―Keratinocytes
Layers and Cell Types of the Epidermis

16. Epidermal Cells
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In structure, the epidermis consists of four types
of cells:
keratinocytes, melanocytes, Merkel cells, and
Langerhans cells
1.Keratinocytes: specialized cells that produce
the protein keratin,
―keratin toughens and waterproofs the skin.
―are the predominant cell type of the epidermis.
❑Keratinization: the process by which the nucleiof
keratinocytes degenerateand their cellular content
becomes dominated by keratin when they are pushed
away from the vascular nutrient and oxygen supply
of the dermis
▪i.e., keratinocytes of the stratum basaleundergo mitosis and produce new epidermal
cells to replace the dead ones that exfoliate (flake off) from the surface.
▪the process produce outer layer that resists abrasion and forms permeability layer.

17. Epidermal Cells cont.
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2.Melanocytes: specialized epithelial cells that
synthesize the pigment melanin
―melanin provides a protective barrier to the ultraviolet
radiation in sunlight.
―melanin also contribute to skin color
3.Dendritic (Langerhans’) cells: are macrophages
that arise in the bone marrow but migrate to the
stratified squamous epithelia of the epidermis (also the
oral cavity, esophagus, and vagina).
―the epidermis has as many as 800dendritic cells per
square millimeter.
―help to protect the body against pathogens by capturing foreign matter and
“presenting” it to the immune system for a response
4.Tactile (Merkel’s) cells: arerelatively few in number,
―are receptors for the sense of touch, light and pressure

18. Strata of the Epidermis
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The epidermis usually consists of four zones (five in
thick skin; palms and soles) described here in order
from deep to superficial.
1.Stratum Basale (basal layer):
―Deepest portion of epidermis and
―Consists of a single layer of cells in contact with the
dermis
―High mitotic activity
2.Stratum Spinosum (spiny layer):
―Limited cell division
―The deepest cells undergo mitosis and contribute to the replacement of
epidermal cells that exfoliate from the surface.
―Because there is limited mitosis in the stratum spinosum, this layer and the
stratum basaleare collectively referred to as the stratum germinativum

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3.Stratum Granulosum (granular layer):
―consists of only three or four flattened layers of
cells.
―these cells are more in thick skin than in thin
skin.
―these cells contain granules that are filled with
keratohyalin, a chemical precursor to keratin.
4.Stratum Lucidum (clear layer):
―a thin, clear zone that exists only in the lips and
in the thickened skin of the soles and palms.
―the cells have no nuclei or other organelles.
Strata of the Epidermis cont.

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5.Stratum Corneum (hornlike layer):
―Consists of 25 to 30 layers of dead, flattened
(squamous) scalelike, keratinized cells.
―Most superficial and consists of cornified cells
that actually protects the skin.
▪Cornification, brought on by keratinization, is
the drying and flattening of the stratum
corneum
▪is an important protective adaptation of the
skin.
―Those at the surface flake off (exfoliate or
desquamate) as tiny scales called dander, only
to be replaced by new ones from deeper layers.
▪Dandruff is composed of clumps of dander
stuck together by oil from the scalp
Strata of the Epidermis cont.

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Layers of the Epidermis

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Epidermal Layers and Keratinization

23. THE DERMIS
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Thedermismight be considered
the “core” of the integumentary
system (derma–= “skin”),
―as distinct from the epidermis
(epi–= “upon” or “over”) and
―hypodermis(hypo–= “below”).
The dermis is the underlying
connective tissue layer that
supports the epidermis.
―it is deeper and thicker than the epidermis
―it ranges from 0.2 mm thick in the eyelids to about 4 mm thick in the palms and soles.
The dermis is tightly connected to the epidermis by a basement membrane .
―is a narrow, undulating, multi-layered structure lying between the epidermis and
dermis, which supplies cohesion between the two layers

24. Function of the Dermis
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Situated between the basement
membrane zone and the subcutaneous
layer, the primary role of the dermis is to
sustainand supportthe epidermis.
The main functions of the dermis are:
―Protection;
―Cushioningthe deeper structures
from mechanical injury (strain and
stress)
―Providing nourishmentto the
epidermis;
―Playing an important role in wound
healing.

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The dermis is composed;
❖mainly of collagen (70% of the dermis)
―gives the skin its toughness and
strength
―binds water (hydrate skin)
❖but also contains elastic fibers
―elastic fibers give the skin its
elasticity and are responsible for the
stretch-recoil (enabling movement)
properties of skin
Structures in the Dermis
❖muscular tissue
―smooth muscle (piloerector muscles) associated with hair follicles contract in
response to stimuli, such as cold, fear, and touch –goose bumps
―In the face, skeletal muscles attach to dermal collagen fibers and produce
such expressions as a smile, a wrinkle of the forehead, and the wink of an eye.

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❖well supplied with blood vessels,
―supply nutrients to the mitotically active stratum basaleof
the epidermis and to the cellular structures of the dermis,
such as glands and hair follicles.
―play an important role in regulating body temperature and
blood pressure
▪autonomic vasoconstriction or vasodilation responses can
either shunt the blood away from the superficial dermal
arterioles or permit it to flow freely throughout dermal
vessels
▪fever or shock can be detected by the color and
temperature of the skin
―bedsores, or decubitus ulcer
▪bedsores are most common on skin overlying a bony
projection, such as at the hip, ankle, heel, shoulder, or
elbow
Structures in the Dermis cont.
FIGURE: A bedsore (decubitus ulcer)
on the medial surface of the ankle.

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❖well supplied with nerve endings (innervation
of the skin)
―sensory perception serves a critically important
protectiveand social/sexual function.
―several types of free sensory nerve endings that
respond to various temperature, tickle, or
pain stimuli.
―there are also specialized receptors;
▪Pacinian corpuscles that detect pressure
and vibration; and
▪Meissner’s corpuscles(tactile or touch
receptors) which are touch-sensitive.
Structures in the Dermis cont.
―certain areas of the body, such as the palms, soles, lips, and external genitalia, have a
greater concentration of sensory receptors and are therefore more sensitive to touch.
―the autonomic nerves supply the blood vessels and sweat glands and arrector pili
muscles (attached to the hair)

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❖well supplied with lymph vessels, sweat glands, sebaceous glands
―lymphatic drainage of the skin is important, as they function to conserve
plasma proteins and scavengeforeign material, antigenic substances and
bacteria
❖hair follicles, andnail roots are also embedded in dermis
❖Cells include: fibroblasts, macrophages, mast cells, WBC’s
―Fibroblastis the major cell type of the dermis and its main function is to
synthesize collagen, elastin and the viscous gel within the dermis.
―Mast cells contain granules of vasoactive chemicals (the main one being
histamine).
▪They are involved in moderating immune and inflammatory responses in
the skin
Structures in the Dermis cont.

29. Layers of Dermis cont.
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The dermis is structurally made of two layers of
connective tissue(papillary andreticular
layer) that compose an interconnected mesh of
elastin and collagenous fibers, produced by
fibroblasts
1.Stratum papillarosum(papillary layer):
―a thin superficial area of loose, areolar tissue
adjacent to (in contact with) the epidermis
―accounts for about one-fifth of the entire dermis
―rich in small blood vessels
(c) Reticular layer of dermis
(b) Papillary layer of dermis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) layers of the dermis
―allows for mobility of leukocytes and other defense cells should
epidermis become broken
―also contains phagocytes, lymphatic capillaries, fibroblasts, mast cells,
a small number of fat cells (adipocytes), nerve fibers, and touch
receptors (Meissner corpuscles).

30. Papillary Layer cont.
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Numerous finger-like projections, called dermal
papillae, extend from the upper portion of the dermis
into the epidermis.
―this dermal and epidermal boundaries thus interlock
(interdigitates),
―an arrangement that strengthens the connection
between the two layers of skin,
▪resists slippage of the epidermis across the dermis
―dermal papillae also contain capillary loops
supplying the epidermis with nutrients and oxygen.
Papillae form the base for the friction ridges
(contours in the skin's surface) on the palms,
fingers, soles, and toes
―genetically and epigenetically determined and
are therefore unique to the individual,
―the ridges of fingerprints function to prevent
slippage when grasping objects.
Epidermal ridges occur in patterns (e.g., fingerprint)

31. Layers of Dermis cont.
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2.Stratum reticularosum(reticular layer):
a much thicker region which lies deep in the
papillary region
is composed of dense irregular connective
tissue
thicker collagenous, elastic, and reticular
fibers that weave throughout it.
i.e., appears reticulated (net-like) due to a
tight meshworkof fibers (elastin and
collagen fibers)
(c) Reticular layer of dermis
(b) Papillary layer of dermis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) layers of the dermis
This layer is well vascularizedand has a rich sensory and
sympathetic nerve supply.
Also located within the reticular region are sebaceous glands, sweat
glands, receptors, larger blood vessels, and the roots of hairs, and nails.

32. Reticular Layer of Dermis cont.
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The protein fibresgive the dermis its
properties of strength, extensibility, and
elasticity.
It is quite distensible, as is evident in
pregnant women or obeseindividuals,
but it can be stretched too far, causing
“tearing” of collagen fibers of the dermis.
The repair of a strained dermal area leaves a
white streak called a striae (stretch mark),
or lineaalbicans
Linea albicans occur especially in areas
most stretched by weight gain: the thighs,
buttocks, abdomen, and breasts.
FIGURE: Stretch marks (lineaealbicantes)
on the abdomen of a pregnant woman.
Stretch marks generally fade with time but
may leave permanent markings.

33. The Dermis cont.
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Elastic and collagenous fibers within the
dermis are arranged in definite patterns,
producing lines of tension (cleavage)
in the skin and providing skin tone.
Cleavage (tension) lines are important in
surgery
―If incision is made parallel to lines,
there is less gapping, faster healing,
less scar tissue
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34. THE HYPODERMIS
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The hypodermis (subcutaneous
layer, or superficial fascia, or
subcutis) is a layer directly below
the dermis.
As superficial fascia it serves to
connect the skin to the underlying
fascia (fibrous tissue) of the bones
and muscles.
as well as supplying it with blood
vessels and nerves
fasciais a band or sheet of
connective tissue, primarily
collagen, beneath the skin that
attaches, stabilizes, encloses, and
separates muscles and other
internal organs

35. The Hypodermis cont.
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The hypodermis is strictly not a part of the skin,
―although the border between the hypodermis and dermis can be difficult to
distinguish
―and it also provides the main structural support for the skin
The hypodermis consists of;
―well-vascularized, loose, areolar connective tissue
―largely (50% of body fat) of adipose tissue, which functions
▪as a mode of fat storage
▪provides insulation from cold,
▪pads the body,
▪cushioning (shock absorption) for the integument to protect underlying
structures from trauma
▪regulate temperature
―the main cell types are fibroblasts, macrophages and adipocytes

36. The Hypodermis cont.
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Obesity is due mainly to the accumulation of subcutaneous fat.
―the subcutaneous fat is about 8% thicker in women than in
men and differs in distribution between the sexes
The hypodermis is the site for subcutaneous injections.
―because the subcutaneous tissue is highly vascular.
Figure: Distribution of Subcutaneous
Fat in Males and Females
Unlike muscle, subcutaneous
tissue does not have a rich blood
supply, and absorption of drugs is
therefore slower than via the
intramuscular route.
―This slower rate of absorption is
beneficial when continuous
absorption of a drug is required;
▪for example, with insulin or
heparin

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Summary of the Layers of the Skin

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39. Coloration of the Skin
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Human skin shows high skin
colourvariety from the darkest
brown to the lightest pinkish-white
hues.
Human skin shows higher
variation in colourthan any
mammalian species
Results from combination of
evolutionary selection pressures
―especially differences in
exposure to ultraviolet radiation
(UVR)
―evolved to primarily regulate
the amount of ultraviolet
radiation (UVR) penetrating the
skin, controlling its biochemical
effects

40. Coloration of the Skin cont.
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Normal skin color is the expression of a combination of three pigments:
melanin, carotene, and hemoglobin.
❑Melanin:
Most significant factor in determining human skin color
―produced by melanocytes
―accumulate in the keratinocytes of stratum basaleand stratum spinosum
―transferred into the keratinocytes via a cellular vesicle called a melanosome
Melanin occurs in two primary forms:
―eumelanin; exists as black and brown (brownish black)
―pheomelanin; a reddish yellow sulfur-containing pigment (provides a red color)
Increased melanin accumulation protects
―the DNA of epidermal cells from UV ray damage and
―the breakdown of folic acid, a nutrient necessary for our health and well-being.

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Figure: Skin Pigmentation.The relative coloration of the skin
depends of the amount of melanin produced by melanocytes in
the stratum basaleand taken up by keratinocytes.
In contrast, too much melanin can interfere
with the production of vitamin D,
―important nutrient involved in calcium
absorption.
Thus, the amount of melanin present in our
skin is dependent on a balance between
―available sunlight and folic acid
destruction, and
―protection from UV radiation and vitamin
D production.
Skin colouris determined not by the
number of melanocytes,
―but by the number andsize of the
melanosomes
Coloration of the Skin cont.:
melanin cont.

42. Coloration of the Skin cont.:
melanin cont.
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People of different skin colors have the same number of melanocytes
―dark skinned people
▪produce greater quantities of melanin and accumulate in keratinocytes
▪melanin granules in keratinocytes more spread out than tightly clumped
▪melanin breaks down more slowly
▪melanized cells seen throughout the epidermis
―light skinned people
―melanin clumped near keratinocyte nucleus
―melanin breaks down more rapidly
―little seen beyond stratum basale
Amount of melanin also varies with exposure to ultraviolet (UV) rays of sunlight
―UVR accounts for up to 77% of variation in human skin color

43. Coloration of the Skin cont.:
melanin cont.
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UVR has two adverse effects:
―causes skin cancer
―breaks down folic acid needed for normal cell division, fertility, and fetal
development
UVR has a desirable effect:
―stimulates keratinocytes to secrete chemicals that stimulate melanocytes to
manufacture melanin and built up in keratinocytes
―stimulates synthesis of vitamin D necessary for dietary calcium absorption
Ancestral skin color is a compromise between vitamin D and folic acid requirements
―populations native to the tropics and their descendants tend to have well-
melanized skin to screen out excessive UVR
―populations native to far northern or southern latitudes where the sunlight is
weak, tend to have light skin to allow for adequate UVR penetration

44. Other Factors in Skin Color
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2.Hemoglobin: is not a pigment of the skin; rather, it is the oxygen-binding
pigment found in red blood cells.
―Oxygenated blood flowing through the dermis gives the skin (e.g., the lips,
where blood capillaries come closer to the surface) its pinkish tones.
―typical of Caucasian skin
3.Carotene: yellow pigment acquired from egg yolks and yellow/orange (e.g.,
carrots) vegetables
―tends to concentrates in stratum corneum and subcutaneous fat
Women have skin averaging about 4% lighter than men
―need greater amounts of vitamin D and folic acid to support pregnancy and
lactation
High altitude and dry air increases skin pigmentation
―Andes, Tibet, Ethiopia

45. Abnormal Colors of Diagnostic Value
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Certain physical conditions or diseases cause symptomatic discoloration of the skin.
❑Cyanosis is blueness of the skin resulting from a deficiency of oxygen in the
circulating blood.
―appears in people with certain cardiovascular or respiratory diseases.
―result from conditions that prevent the blood from picking up a normal load of oxygen in
the lungs, such as airway obstructions in drowning and choking, lung diseases such as
emphysema, or respiratory arrest
❑Erythemais abnormal redness of the skin.
―is caused by increased blood flow in dilated cutaneous blood vessels
―occurs in such situations as exercise, hot weather, sunburns, anger, and
embarrassment.
❑Jaundiceis a yellowing of the skin and whites of the eyes resulting from high levels of
bilirubin in the blood.
―is usually symptomatic of liver dysfunction and sometimes of liver immaturity, as in a
jaundiced newborn.

46. Abnormal Colors Of Diagnostic Value cont.
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❑Palloris a pale or ashen color that occurs when there is so little blood flow
through the skin that the white color of the dermal collagen shows through.
―it can result from emotional stress, low blood pressure, circulatory shock,
cold temperatures, or severe anemia.
❑Albinismis a genetic lack of melanin that results in white hair, pale skin,
and pink eyes.
―melanin is synthesized from the amino acid tyrosine by the enzyme
tyrosinase.
―people with albinism have inherited a recessive, nonfunctional tyrosinase
allele from both parents
A hematomaor bruise, is a mass of clotted blood showing through the skin.
―it is usually due to trauma (blows to the skin)

47. SECTION4: FUNCTIONS OFTHESKIN
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NOBRANCHOFSCIENCEHITSASCLOSETOHOMEASTHESCIENCEOFOUROWNBODIES
❑Chapter Objectives:
By the end of this section, you will be able to:
Discuss the role of the skin in
➢the protection of the body from disease and external injury,
➢the regulation of body fluids and temperature,
➢absorption,
➢synthesis,
➢sensory reception, and communication.
Describe some common clinical conditions of the skin that result from
nutritional deficiencies or body dysfunctions.

48. FUNCTIONS OF THE SKIN
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The skin is much more than a container for the body.
It has a wide variety of important functions:
❑Basic Functions of the Skin
Protect the body's internal living tissues and organs: acts as the body's first
line of defense (barrier) against;
―Mechanical damage (bumps & cuts); trauma
―Chemical damage (acids & bases)
―Thermal damage (heat/cold)
―Infection (infectious organisms); e.g., Bacteria
―UV radiation
―Desiccation (drying out) or dehydration; waterproofing

49. Basic Functions of the Skin cont.
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Temperature regulation (sweat glands); protect the body against abrupt
changes in temperature,
―maintain homeostasis
Transdermal absorption; administration of several medicines as ointments or
lotions steadily through thin skin
―or by means of adhesive patches that release the medicine steadily through a
membrane;
―e.g., treatment of inflammation with a hydrocortisone ointment, and use of
nitroglycerine patches to relieve heart pain
Synthesize Vitamin D through exposure to ultraviolet light
Sensory reception (touch, heat, pain, pressure)
Help excrete waste materials through perspiration; e.g., urea
Immunity
Maintenance of the body form
Formation of new cells from stratum germinativum to repair minor injuries

50. SECTION5: EPIDERMAL DERIVATIVES
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NOBRANCHOFSCIENCEHITSASCLOSETOHOMEASTHESCIENCEOFOUROWNBODIES
❑Chapter Objectives:
By the end of this section, you will be able to:
Identify the accessory structures of the skin
Describe the structure of hair and list the three principal types.
Discuss the structure and function of nails.
Compare and contrast the structure and function of the three
principal kinds of integumentary glands.

51. EPIDERMAL DERIVATIVES
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Accessory structures (appendages or epidermal derivatives ) of the skin include
hair, nails, andcutaneous orintegumentary glands (i.e., sweat glands, and
sebaceous glands).
―these structures embryologically originate from the epidermis (ectodermal
derivation) and
―can extend down through the dermis into the hypodermis.
Hair and nails are composed mostly of dead, keratinized cells (hard keratin).
―while the stratum corneum of the skin is made of pliable soft keratin
Hair and nails are structural features of the integument and have a limited
functional role.
―by contrast, integumentary glands are extremely important in body defense and
maintenance of homeostasis.

52. Human Hair
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Hair is a slender filament of dead, keratinized cells that grows out of the
epidermis.
―Strands of hair originate in an epidermal penetration (an oblique tube) of the
dermis called the hair follicle.
Hair is found everywhere on the body except the;
―lips, nipples, parts of the genitals,
―palmar (palms) and plantar (soles) skin,
―lateral and ventral surfaces of the fingers and toes
Men and women have about the same density of hair on their bodies,
―but hair is generally more obvious on men as a result of male hormones.
Number of hairs does not differ much from person to person or even between sexes
―differences in appearance due to texture and pigmentation of the hair

53. Types of Human Hair
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Not all hair is alike, even on one person.
―Over the course of our lives, we grow three kinds of hair:
❑lanugo–fine, downy, unpigmented hair that appears on the fetus in the last three
months of development
❑vellus–fine, pale hair that replaces lanugo by time of birth
―two-thirds of the hair of women
―one-tenth of the hair of men
―all of hair of children except eyebrows, eyelashes, and hair of the scalp
❑terminal–longer, coarser, and usually more heavily pigmented
―forms eyebrows, eyelashes, and the hair of the scalp
―after puberty, forms the axillary and pubic hair
―male facial hair and some of the hair on the trunk and limbs

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Structure of Hair and Follicle
Hair is divisible into three zones along its
length
1.shaft–is the visible, but dead, portion of the
hair
―not anchored to the follicle, and
―much of this is exposed at the skin’s
surface.
2.root–the remainder of the hair which is
anchored in the follicle
―lies below the surface of the skin
3.bulb–is the enlarged base of the root within the hair follicle.
―originates deep in the dermis or hypodermis
―includes a layer of living mitotically active basal cells called the hair matrix
―hair bulb surrounds the hair papilla

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Structure of Hair and Follicle cont.
Dermal papilla –a bit or bud of
vascular connective tissue that grows
into the bulb
―contains blood capillaries and nerve
endings from the dermis
―provides the hair with its sole
source of nutrition
Hair matrix –region of mitotically active basal cells immediately above papilla
―hair’s growth center
In cross section, a hair reveals three layers:
1.Medulla: centralcore of loosely arranged cells and air spaces
2.Cortex: constitutes the bulk of the hair and surrounds the medulla
―consists of several layers of compressed elongated keratinized cells
3.Cuticle: composed of multiple layers of very thin, hard, and scaly keratinized
cells that overlap each other; surrounds the cortex

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Structure of the Hair and Follicle cont.
The follicleis a diagonal tube that dips
deeply into the dermis and sometimes extends
as far as the hypodermis.
―The hair follicle is made of multiple layers
of cells that form from basal cells in the
hair matrix and the hair root.
Associated with the follicle are nerve and
muscle fibers.
―hair receptors: nerve fibers that entwine
each follicle
▪respond to hair movement
Also associated with each hair is a piloerector muscle (arrector pili):
―bundles of smooth muscle cells
―makes the hair stand on end in response to cold, fear, or other stimuli,
―causes goose bumps; pulls the follicles into a vertical position

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Hair Growth and Loss
Hair grows fastest from adolescence until the 40s.
Each hair developsfrom stratum basalecells within the bulb of the hair, where
nutrients are received from dermal blood vessels.
―as the cells divide, they are pushed away from the nutrient supply toward the
surface,
―and cellular death andkeratinization occur
The life spanof a hair varies from 3 to 4 months for an eyelash to 3 to 4 years for
a scalp hair.
―each hair lost is replaced by a new hair that grows from the base of the follicle and
pushes the old hair out.
―between 10 and 100 hairs are lost daily.

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Alopecia:is thinning of the hair or baldness
Pattern baldness: is the condition in which hair loss from specific regions of the
scalp rather than thinning uniformly across the entire scalp
―results when hair is lost and not replaced
―may be disease-related, but it is generally inherited by combination of geneticand
male sex hormone testosterone influence
―baldness allele is dominant in males and expressed only in high testosterone levels
―testosterone causes terminal hair in scalp to be replaced by vellus hair
Hirsutism:a condition of excessive or undesirable hairiness in areas that are not
usually hairy
―especially in women (as they experience hormonal changes during menopause) and
children
―tends to run in families and usually results from either masculinizing ovarian
tumors or hypersecretion of testosterone by the adrenal cortex
Hair Growth and Loss cont.

59. Function of Hair
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The primary function of hair is protection, even though its effectiveness is limited.
Hair on the scalp and eyebrows protect against sunlight (sunburn).
―Hair on the scalp may also protect against mechanical injury, and helps retain
heat
The eyelashes and the hair in the nostrils protect against airborne particles.
―guard hairs (vibrissae) -guard nostrils and ear canals
Hair receptors alert us of parasites crawling on skin
Some secondary functions of hair are to;
―to distinguish individuals (gender identification)
―to serve as a sexual attractant: pubic and axillary hair signify sexual maturity
and aids in transmission of sexual scents
―nonverbal communication

60. Nails
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Fingernails andtoenails are clear, hard derivatives of (formed from) the
stratum corneum.
―They are composed of very thin, dead, scalelike cells, densely packed
together and filled with parallel fibers of hard keratin
Fingernails grow at a rate of about 1 mm per week and toenails somewhat
more slowly
―New cells are added to the nail plate by mitosis in the nail matrix at
its proximal end.
Both fingernails and toenails function;
―to protect the digits, and
―fingernails also aid in grasping and picking up small objects, and other
manipulations
―flat nails allow for more fleshy and sensitive fingertips

61. Structure of Nails
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Each nail consists of a body, free border (edge),
andhidden border.
The most important anatomical features of a nail
are the;
―nail matrix;a growth zone concealed beneath
the skin at the proximal edge of the nail,
―nail plate; which is the visible portion covering
the fingertip.
▪it rests on a nail bed, which is actually the
stratum spinosum of the epidermis.
▪the body and nail bed appear pinkishbecause
of the underlying vascular tissue.
The sides of the nail body are protected by a nail
fold, and the furrow between the sides and body is
the nail groove.

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Structure of Nails cont.

63. Nails cont.
63
The condition of nails may be indicative of a person’s general health and well-
being
the appearance of the nails can therefore be valuable to medical diagnosis.
For example;
―a yellowish hue may indicate certain glandular dysfunctions or nutritional
deficiencies.
―split nails may also be caused by nutritional deficiencies.
―a prominent bluish tint may indicate improper oxygenation of the blood.
―spoon nails (concave body) may be the result of iron-deficiency anemia,
―clubbing at the base of the nail may be caused by lung cancer
―clubbing the nails and fingertips in conditions of long-term hypoxemia
(deficiency of oxygen in the blood) resulting from congenital heart defects
and other causes.
―dirty or ragged nails may indicate poor personal hygiene, and chewed nails
may suggest emotional problems.
F1
F2
F3
F5
F4

64. Cutaneous Glands
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All of the glands of the skin are located in the dermis,
where they are physically supported and receive nutrients.
―although they originate in the epidermal layer
Glands of the skin are referred to as exocrine,
because they are externally secreting glands that
either release their secretions directly or through ducts.
The glands of the skin are of three basic types:
1.sebaceous (se˘-ba'shus),
2.sudoriferous (soo''dor-if'er-us); merocrine and apocrine
sweat glands,
3.ceruminous (se˘-roo'mı˘-nus), and the
―mammary glands.

65. Sebaceous Glands
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Sebaceous glands (oil glands) are associated with hair follicles,
They secrete sebum(consists mainly of lipids) onto the shaft of the hair
―exceptions: lips, meibomian glands of eyelids, genitalia
Sebum dispersed to the surface of the skin, where it
―lubricates and waterproofs the stratum corneum and
―also prevents the hair from becoming brittle
If the ducts of sebaceous glands become blocked for some reason, the glands may
become infected, resulting in acne.
Sex hormones regulate the production and secretion of sebum,
―hyperactivity of sebaceous glands can result in serious acne problems,
particularly during teenage years.

66. Sudoriferous Glands
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Sudoriferous glands excrete perspiration, or sweat, onto the surface of the skin
Two kinds of sweat (sudoriferous) glands
a)merocrine (eccrine) sweat glands:
―most numerous skin glands -3 to 4 million in adult skin
―watery perspiration that helps cool the body
―numerous in palms and soles. Absent from margin of lips, labia minora, tips of penis, and
clitoris
b)apocrine sweat glands:
―Found in axillae, genitalia (external labia, scrotum), around anus
―occur in groin, anal region, axilla, areola, bearded area in mature males
―ducts lead to nearby hair follicles
―produce sweat that is thicker, milky, and contains fatty acids
―scent glands that respond to stress and sexual stimulation
―develop at puberty
―Pheromones; chemicals that influence the physiology of behavior of other members of the
species
―Bromhidrosis; disagreeable body odor produced by bacterial action on fatty acids

67. Ceruminous Glands
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Ceruminous Glands are simple, coiled tubular glands with ducts that lead to skin
surface
They are found only in external ear canal (auditory meatus)
their secretion combines with sebumand dead epithelial cells to form earwax
(cerumen)
―keep eardrum (tympanic membrane) pliable
―waterproofs the canal
―kills bacteria
―makes guard hairs of ear sticky to help block foreign particles (dirt and insects)
from entering auditory canal

68. Mammary Glands
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Breasts (mammae) of both sexes contain very
little glandular material
Mammary glands –milk-producing glands
that develop only during pregnancy and
lactation
―modified apocrine sweat (sudoriferous) gland
―richer secretion released by ducts opening
into the nipple
The breasts of the female reach their greatest
development during the childbearing years,
―under the stimulus of pituitary and ovarian
hormones.

69. Aging of the Skin
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As the skin ages, it becomes thin and dry, and begins to lose its
elasticity.
―collagenous fibers in the dermis become thicker and stiffer, and
―the amount of adipose tissue in the hypodermis diminishes,
making it thinner.
―This leads to;
▪wrinkling, or permanent infoldings of the skin, becomes
apparent
▪skin not as well protected from the sun
▪skin more easily damaged
The number of active hair follicles, sweat glands, and sebaceous
glands also declines
―leads reduced sweating, and decreased sebum production
Melanocytes that produce melanin gradually atrophy.
this accounts for graying of the hair and pallor of the skin.
FIGURE: Aging of the skin results in a loss
of elasticity and the appearance of wrinkles.

70. Clinical Considerations
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The skin is a buffer
against the external
environment
It is therefore subject
to a variety of
disease-causing
microorganisms
and
physical
assaults.

71. Burns
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A burn is an epithelial injury caused by contact with a thermal, radioactive,
chemical, or electrical agent.
Burns generally occur on the skin,
―but they can involve the linings of the respiratory and GI tracts.
The extent and location of a burn is frequently less important than the degree to
which it disrupts body homeostasis.
―Burns that have a local effect (local tissue destruction) are not as serious as
those that have a systemic effect.
―Possible systemic effects include body dehydration, shock, reduced
circulation andurine production, andbacterial infections.
Burns are the leading cause of accidental death.
―burn deaths result primarily from fluid loss, infection, and the toxic effects of
eschar (ESS-car)—the burned, dead tissue.

72. Burns cont.: Classification
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Burns are classified
as first degree,
second degree, or
third degree, based
on their severity
FIGURE: The classification of burns, (a) First-degree burns involve the epidermis and are characterized
by redness, pain, and edema—such as with a sunburn;
(b) second-degree burns involve the epidermis and dermis and are characterized by intense pain, redness,
and blistering; and
(c) third-degree burns destroy the entire skin and frequently expose the underlying organs. The skin is
charred and numb and does not protect against fluid loss.

73. Skin Grafts
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A skin graft is a segment of skin that
has been excised from a donor site
and transplanted to the recipient site,
or graft bed.
―an autograftis the most
successful type of tissue transplant
―a heterotransplant(xenograph;
between two different species) can
serve as a temporary treatment to
prevent infection and fluid loss.
FIGURE: A skin graft to the neck. (a) Traumatized skin is prepared for excision;
(b) healthy skin from another body location is transplanted to the graft site; and (c) 1
year following the successful transplant, healing is complete.
Skin graft is performed to heal wounds where
―extensive areas of the stratum basaleof the epidermis are destroyed in
second-degree or third-degree burns or frostbite,
―new skin cannot grow back

74. Skin Grafts cont.
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A skin graft is a segment of skin that
has been excised from a donor site
and transplanted to the recipient site,
or graft bed.
―an autograftis the most
successful type of tissue transplant
―a heterotransplant(xenograph;
between two different species) can
serve as a temporary treatment to
prevent infection and fluid loss.
Skin graft is performed to heal wounds where
―extensive areas of the stratum basaleof the epidermis are destroyed in
second-degree or third-degree burns or frostbite (local destruction of the
skin resulting from freezing),
―new skin cannot grow back

75. Skin cancer
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Skin cancer is induced by the ultraviolet rays of the sun.
―occurs most often on the head and neck, where exposure to the sun is
greatest.
―most common in fair-skinned people and the elderly, who have had the
longest lifetime UV exposure
―one of the most common cancers but one of the easiest to treat
―has one of the highest survival rates if detected and treated early
There are three types of skin cancer named for the epidermal cells in
which they originate:
―basal cell carcinoma; forms from cells in stratum basale
▪most common type
▪least dangerous because it seldom metastasizes
―squamous cell carcinoma; arise from keratinocytes from stratum
spinosum
▪tends to metastasize to lymph nodes and may become lethal
―malignant melanoma; arises from melanocytes
▪less than 5% of skin cancers, but most deadly form

76. Wound Healing
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The skin effectively protects against many abrasions,
―but if a wound does occur a sequential chain of events
promotes rapid healing.
The process of wound healing depends on the extentand
severity of the injury.
―Trauma to the epidermal layers stimulates increased
mitotic activity in the stratum basale,
―whereas injuries that extend to the dermis or
subcutaneous layer elicit activity throughout the body,
not just within the wound area.
FIGURE: Various kinds of wounds: (a)
puncture, (b) abrasion, (c) laceration, and
(d ) avulsion.
If the wound is severe enough, the granulation tissue may develop into scar tissue.
―the collagenous fibers of scar tissue, are more dense than those of normal tissue,
―scar tissue has no stratified squamous or epidermal layer
―Scar tissue also has fewer blood vessels than normal skin,
―may lack hair, glands, and sensory receptors.

77. Wound Healing cont.
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FIGURE: The process of wound
healing.
(a) A penetrating wound into the dermis
ruptures blood vessels.
(b) Blood cells, fibrinogen, and fibrin
flow out of the wound.
(c) Vessels constrict and a clot blocks
the flow of blood.
(d) A protective scab is formed from the
clot, and granulation occurs within the
site of the wound.
(e) The scab sloughs off as the
epidermal layers are regenerated.