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Reticular tissue

Section of lymph node, 400x

Dense irregular connective tissue

Section of dermis, 200x

Dense regular (collagenous) connective tissue

Section of tendon, 200x

Dense regular (elastic) connective tissue

Section of tunica media of aorta, 400x

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The supporting tissue category consists of the skeletal tissues — cartilage and bone. Like the connective tissues, the supporting tissues have

relatively few cells surrounded by a signifi cant amount of extracellular

Supporting Tissue

matrix, which for the most part the cells produce. However, unlike the soft matrix of the connective tissues, the extracellular

matrix of the supporting tissues is fi rm and rubber-like in cartilage and hard in bone tissue.

Hyaline cartilage

Section of cartilage in developing fetal bone, 200x

Fibrocartilage

Section of intervertebral disc, 200x

Elastic cartilage

Section of cartilage from auricle of ear, 400x

 1 Hyaline ground substance

 2 Collagen fibers in ground substance

 3 Elastic fibers in ground substance

 4 Chondrocyte nucleus

 5 Chondrocyte in lacuna

 6 Perichondrium

 7 Bone trabecula

 8 Osteocyte

 9 Red bone marrow

10 Canaliculi

 11 Lacuna

12 Lamella

13 Central canal

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Spongy bone

Section of epiphysis of metacarpal bone, 200x

Compact bone

Section of diaphysis of fibula, 100x; callout of osteon, 400x

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is a greater percentage of the tissue then are the cells. However, the extracellular matrix of blood and lymph is a liquid matrix called plasma, rather than the soft, fi rm matrix of connective tissues. The most recent Terminologia Histologica places

blood and lymph in their own subcategory called the hematolymphoid complex.

Hematolymphoid Complex The tissues blood and lymph traditionally were

classifi ed as connective tissues because, like

all connective tissues, the extracellular matrix

Blood smear

Wright’s stain, 200x; enlargement, 630x; individual cells, 1500x

 1 Erythrocyte or red blood cell (rbc)

 2 Leukocyte or white blood cell (wbc) - neutrophil

 3 Leukocyte or white blood cell (wbc) - monocyte

 4 Thrombocyte (platelet)

 5 Plasma

 6 Crenated red blood cell 2

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(shortening). The names of the different types of muscle tissues arise from the arrangement of the contractile proteins

within their cells. In some tissues the protein arrangement gives the cell a striated, or striped, appearance (striated muscle),

while in other tissues the striped appearance is not evident (non-striated or smooth muscle).

Muscle cells are long, slender cells that have special arrangements of the proteins

actin and myosin within the cytoplasm. The architectural design of these proteins

forms the muscle cell “machinery” that allows the cell to specialize at contracting

Smooth (nonstriated) muscle tissue

Longitudinal section of muscular wall of intestine, 500x

Skeletal striated muscle tissue

Section of vastus lateralis muscle, 400x

Cardiac striated muscle tissue

Section of ventricle of heart, 500x

 1 Nucleus

 2 Sarcoplasm

 3 Smooth muscle cell

 4 Cardiac muscle cell

 5 Skeletal muscle cell

 6 Intercalated disc

Muscle Tissue

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that are involved in protecting, insulating, and nourishing the neurons. The neurons can be grouped together in long slender

structures called nerves, or they can form the complex circuit boards we call the spinal cord and brain.

Nervous tissue forms the complex electrical computing system of the body. The cells

that characterize nervous tissue are the branched, wire-like cells called neurons. Surrounding the neurons of the nervous tissue are the smaller, more numerous glial cells

Nerve Tissue

Nerve tissue

Multipolar neuron smear, 400x

Neuron

400x

Nerve tissue

Section of ventral horn of spinal cord, 200x

 1 Nucleus of multipolar neuron

 2 Cell body of multipolar neuron

 3 Nucleus of glial cell

 4 Axon

 5 Dendrite

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Th e integument forms

the organ system that covers the body. From the Latin

meaning to cover inward, the integument is an important

system that performs a variety of functions that are

 essential to life. Th e outer layers of the integument called

the epidermis and dermis form the skin, which is an

 important protective layer. Th e skin protects the body in

a number of ways. Its tough, outer-covering of dead cells

protects the more delicate deeper layers from friction and

abrasion. Th e pigment cells in the epidermis produce

 melanin, a protective pigment that absorbs damaging ultraviolet radiation from the sun, to protect the rapidly dividing

keratinocytes that make up the majority of the epidermal layer

of the skin. Th e structure of the epidermal layer of the

skin and its secretions also protect the body from excessive water loss or gain. Th e large network of

blood vessels and numerous sweat glands form

an evaporative cooling system that help to protect the body from overheating in warm conditions or during exercise. Additionally, the impenetrable skin and some of its special cells

form a fi rst line of defense against bacterial

invasion.

Th ese are just some of the functions of the

integument. Other important functions are

the following: it is a major surface for sensory

 perception to receive input or stimuli from the

environment, it is an excretory surface to help rid

the body of metabolic wastes, it plays an important

role in energy storage and metabolism, it provides an

important site for the production of vitamin D and various

growth factors, and it plays a major role in sociosexual communication and identifi cation. Th is chapter will depict the

structural features of the integument that account for this

wide variety of important functions.

Find more information

about the integument in

3 Integument

17

REAL ANATOMY

18

podermis. The cadaver and histology images on this and the facing page illustrate these two layers of anatomy. The skin,

consisting of the superfi cial epidermis and the deeper dermis, structurally combines an epithelial tissue and connective tissue to form the body’s covering organ. The skin is an organ that produces hairs, various glands, fi nger and toe nails, and

accounts for the majority of the functions of the integument. The subcutaneous layer is a variable layer that can consist of

fat, fi brous connective tissue, loose connective tissue, and smooth muscle.

The integument consists of two major

parts or layers of anatomy, the skin

and the subcutaneous layer, or hySubdivisions of the Integument

Subcutaneous layer of the integument

Anterior view

Epidermal layer of the skin

Anterior view

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 1 Epidermis

 2 Dermis

 3 Subcutaneous layer

 4 Fascia

 5 Periosteum

 6 Compact bone of tibia

 7 Fibula

 8 Medullary cavity

 9 Interosseous membrane

10 Tendon

 11 Muscle

12 Stratified squamous epithelium

13 Dense irregular connective tissue

14 Adipose tissue

15 Retinaculum cutis

16 Secretory coils of sweat gland

Step dissection of leg showing layers of the integument

Anterolateral view Integument

Section of integument, 100x

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my. It can range in thickness from a .10 mm (0.0039 in) on the eyelids to 1.5 mm (0.059 in) on the palms and

soles. Keratinocytes are the primary cells of the epidermis. They proliferate from the stratum basale and differentiate as they push toward the surface, where they even tually form dead cells fi lled with the protein

keratin. Also present in the basal layer are melanocytes that produce the brown pigment melanin to protect

the skin from the ultraviolet radiation from the sun.

The stratifi ed squamous epithelial epidermis is the superfi cial

layer of the skin. This cellular layer and its derivatives — hairs,

nails, and glands — is the most recognizable part of our anatoSkin - Epidermis

Epidermis of integument

100x

Epidermis of skin of a black

Section of thin skin, 200x

Epidermis of skin of a Caucasian

Section of thin skin, 200x

Epidermis of skin of a Caucasian

Section of thick palmar skin, 200x

 1 Stratum basale

 2 Stratum spinosum

 3 Stratum granulosum

 4 Stratum lucidum

 5 Stratum corneum

 6 Connective tissue of dermis

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between the dermis and epidermis is an intricate peg and socket-like arrangement between the two layers.

The dermal pegs are called dermal papillae. This arrangement has multiple functions. It assures that the

two layers are strongly united, it increases the surface area to improve the blood supply to the avascular

epidermis, and it increases the contact surface for sensory receptors. On the palms and soles the arrangement of the dermal papillae creates the friction ridges we call fi ngerprints.

The connective tissue dermis sits deep to the epidermis where it Skin - Dermis forms the strong binding layer of the skin. The zone of interface

Friction ridges (fi ngerprints) of right index fi nger

Anterior view

Dense irregular connective tissue of stratum reticulare

Section of dermis, 200x

Loose connective tissue of stratum papillare

Section of dermis, 200x

 1 Epidermis

 2 Loose connective tissue of

stratum papillare

 3 Dermal papilla of the stratum

papillare

 4 Dense connective tissue of

stratum reticulare

 5 Blood vessel in dermis

 6 Sweat glands in dermis

 7 Longitudinal collagen fibers

 8 Transverse collagen fibers

 9 Friction ridges formed by dermal

papillae

10 Flexion crease line

Dermis of integument

100x

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dermis. This developmental process creates a hair follicle, a baglike extension of the epidermis that projects into the dermis and is

responsible for producing the hair. The hair is a column of dead keratinocytes that arise from the basal keratinocytes at the bottom of

the hair follicle. A sebaceous gland, also derived from the epidermal epithelium, empties into the hair follicle, and a small band of dermal

smooth muscle, the arrector pili muscle, attaches to the base of the follicle. When the muscle shortens it produces “goose bumps” on

the surface of the skin and causes the hair to “stand up.” Nails also arise from invaginations that produce the shallow nail fold and root.

A plate of strongly keratinized tissue emerges from the nail root to cover the dorsal ends of the fi ngers and toes.

During embryonic and fetal development, the epithelial cells of Skin - Hairs and Nails the epidermis push down (invaginate) into the connective tissue

 1 Epidermis

 2 Dermis

 3 Follicle wall

 4 Hair

 5 Papilla

 6 Root of nail

 7 Nail

 8 Nail bed

 9 Lunula

10 Eponychium (cuticle)

 11 Hyponychium

12 Eccrine sweat glands

13 Cartilage

14 Bone

Hair follicle

Section of skin, 100x

Finger of a child

Longitudinal section, 50x

Hair bulb

Section of skin, 400x

Fingernail of an adult

Dorsal view

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Like hairs, glands arise as invaginations of the epidermis into the dermis during

embryonic and fetal life. The three prominent glands of the skin are the sebaceous

gland, the eccrine sweat gland, and the apocrine sweat gland. The sebaceous and

apocrine sweat glands typically empty into a hair follicle, whereas the eccrine sweat

gland empties onto the surface of the epidermis.

Skin - Glands

 1 Sebaceous secretory cells

 2 Eccrine secretory cell

 3 Eccrine duct cell

 4 Apocrine secretory cell

 5 Hair

 6 Hair follicle

 7 Arrector pili muscle

Sebaceous gland

Section of dermis, 200x

Eccrine sweat gland

Section of dermis, 200x

Apocrine sweat gland

Section of thin skin, 200x

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