Dermatology and histology

epidermis: outer layer of the skin

What are the distinct layers of the epidermis?

Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

Where are cells generated in the epidermis?

In the basal layer

What happens to cells as they migrate superficially in the epidermis?

They divide, eventually die, and are sloughed off from the outer layer

What is the lowest layer of the epidermis called?

Basal layer

What type of cells in the epidermis make keratin?

Keratinocytes

What is the function of keratin in the epidermis?

Provides structure, durability, and waterproofing

How often is the full epidermis replaced?

Every month

What type of cells in the epidermis produce melanin?

Melanocytes

What determines the darkness of skin color?

The extent of melanocyte cellular extensions

What type of immune cells are found in the epidermis?

Langerhans cells

What type of sensory cells are found at the boundary of the epidermis and dermis?

Merkel cells

dermis

middle layer of skin

What are the two layers of the dermis?

The two layers of the dermis are the papillary layer and the reticular layer.

What type of connective tissue is found in the papillary layer of the dermis?

The papillary layer contains loose areolar connective tissue.

What is the function of dermal papillae in the thick skin?

Dermal papillae form fingerprints, which help with grip.

What type of connective tissue is found in the reticular layer of the dermis?

The reticular layer contains dense irregular connective tissue.

What percentage of skin thickness does the reticular layer of the dermis account for?

The reticular layer accounts for approximately 80% of skin thickness.

What are the two layers of the dermis?

Outer: loose areolar connective tissue (thin); Inner: dense irregular connective tissue (thick)

What structures are found in the dermis?

Nerves, sensory corpuscles, blood vessels, sweat glands, sebaceous glands, hair follicles

Why do you bleed and feel pain when cuts reach the dermis?

The dermis contains blood vessels and sensory receptors.

What are the types of sensory corpuscles found in the dermis?

Tactile corpuscles (light touch), Lamellar corpuscles (pressure), Hair follicle receptors

What is the hypodermis?

The layer of skin beneath the dermis.

What type of tissue is primarily found in the hypodermis?

Loose connective tissue.

What type of fat is mostly stored in the hypodermis?

Subcutaneous fat.

What are the two main types of connective tissue found in the hypodermis?

Adipose and areolar tissue.

How does subcutaneous fat differ from intra-abdominal fat?

Subcutaneous fat is stored in the hypodermis, while intra-abdominal fat is located within the abdominal cavity.

median cubital vein (or antecubital vein)

The vein of choice because is it large and does not tend to move the the needle is inserted.

cephalic vein

Large vein on the outermost side of the upper arm

basilic vein

large vein on the inner side of the upper arm

thick skin

Covers the palms of the hands and soles of the feet

Has 5 layers of keratinocytes

thin skin

Covers most of the body

Has four layers of keratinocytes

nervous tissue

A body tissue that carries electrical messages back and forth between the brain and every other part of the body.

neuron

a nerve cell; the basic building block of the nervous system

glial cell

cells in the nervous system that support, nourish, and protect neurons

muscle tissue

A body tissue that contracts or shortens, making body parts move. tissue does not push

What is skeletal muscle?

A muscle that is attached to the bones of the skeleton and provides the force that moves the bones.

What are the distinguishing features of skeletal muscle?

Elongated, parallel fibers; multiple, peripheral nuclei (multinucleate); striations.

What are skeletal muscle cells called?

muscle fibers or myofibers

What type of movement is skeletal muscle responsible for?

Voluntary movement.

What does skeletal muscle pull on?

Bone or skin.

What type of muscle tissue is found only in the heart?

Cardiac muscle

Is cardiac muscle voluntary or involuntary?

Involuntary

What are the distinguishing features of cardiac muscle?

Striations, branched cells, single central nuclei (uninucleate)

What are intercalated discs?

Darker striations in cardiac muscle that contain pores allowing chemical signals to pass between cells

What is the function of cardiac muscle?

Involuntary, regular, coordinated contractions

How are chemical signals communicated in cardiac muscle?

Through intercalated discs

What type of muscle is smooth muscle?

Involuntary muscle

Where is smooth muscle found?

Inside many internal organs of the body

What are the distinguishing features of smooth muscle?

Non-striated, tapered short cells, single central nucleus

What type of control does smooth muscle have?

Involuntary control

What does smooth muscle line?

The walls of hollow organs and blood vessels

What is the function of smooth muscle?

Squeezes contents of hollow organs

epithelial tissue

A body tissue that covers the surfaces of the body, inside and out.

• Functions in:

• Protection (covering organ surfaces)

• Absorption/diffusion/transport

• Secretion (glands)

squamous cell

flat, scale-like epithelial cell

Protective surfaces

• Examples: skin, esophagus

• Smaller and easier to replace than cuboidal or columnar cells

• Thin membranes

• Examples: alveoli, capillaries

• Allow for faster diffusion and passive transport

cuboidal cell

cube shaped cells

function: Absorption and secretion

• Larger cell bodies contain machinery for transport & synthesis

columnar cell

column shaped cells

connective tissue

A body tissue that supports the body and connects all its parts.

Function: support, protection, insulation, energy & fluid storage, internal transport, movement

loose (areolar) connective tissue

type of connective tissue with small amounts of cells, matrix, and fibers; found around blood vessels

adipose tissue

Tissue that stores fat.

dense irregular connective tissue

Function: able to withstand tension exerted in many directions; provides structural strength

Location: fibrous capsules of organs and joints; dermis of the skin; submucosa of digestive tract

dense regular connective tissue

Function: attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction

Location: tendons, most ligaments, aponeuroses

Cartilage

strong connective tissue that supports the body and is softer and more flexible than bone

bone

Dense, hard connective tissue composing the skeleton

extracellular matrix

The chemical substances located between connective tissue cells

What is one function of epithelial tissue?

Protection (covering organ surfaces)

What is another function of epithelial tissue?

Secretion (glands)

What are the two types of epithelial tissue?

Proper epithelium and glandular epithelium

What does proper epithelium do?

Covers body and organ surfaces, both outside and inside

What does glandular epithelium form?

Glands that secrete hormones and other substances

What is the function of endocrine glands?

Secretes hormones into the bloodstream

What is the function of exocrine glands?

Secretes substances into tubes or ducts

What type of membranes do epithelial tissues create?

Selectively permeable membranes

What is a characteristic of epithelial tissue regarding blood supply?

Avascular - No blood supply of their own

How do epithelial tissues obtain their blood supply?

They rely on blood supply from surrounding connective tissue

How quickly do epithelial tissues regenerate?

They regenerate quickly