<< Chapter < Page Chapter >> Page >

View the University of Michigan WebScope at (External Link) to explore the tissue sample in greater detail. If you zoom on the cells at the outermost layer of this section of skin, what do you notice about the cells?

Stratum basale

The stratum basale    (also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The cells in the stratum basale bond to the dermis via intertwining collagen fibers, referred to as the basement membrane. A finger-like projection, or fold, known as the dermal papilla    (plural = dermal papillae) is found in the superficial portion of the dermis. Dermal papillae increase the strength of the connection between the epidermis and dermis; the greater the folding, the stronger the connections made ( [link] ).

Layers of the epidermis

This illustration shows a cross section of the epidermis. The cells of the innermost layer, the stratum basale, are large and have a purple nucleus. The stratum basale curls around the dermis, which projects into the epidermis. The stratum basale contains four layers of large, triangle-shaped keratinocytes. Fibers are visible within the spaces between keratinocytes in the stratum basale. A melanocyte is also present in this layer. The melanocyte possesses finger-like projections extending from its main cell body. The projections branch through the extracellular spaces between nearby keratinocytes. Above the stratum basale is the stratum spinosum which consists of 8 layers of oval-shaped keratinocytes. The nucleus is present in these keratinocytes, but has faded to a lighter purple. The stratum granulosum contains five layers of keratinocytes, each containing spots in its cytoplasm, labeled the lamellar granules. The stratum lucidium contains 4 layers of diamond-shaped cells with no nucleus. The stratum corneum contains 9 layers of keratinocytes with no nucleus , nor cytoplasm. A few of the cells in the topmost layer of the stratum corneum are flaking off from the skin.
The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale is a single layer of cells primarily made of basal cells. A basal cell    is a cuboidal-shaped stem cell that is a precursor of the keratinocytes of the epidermis. All of the keratinocytes are produced from this single layer of cells, which are constantly going through mitosis to produce new cells. As new cells are formed, the existing cells are pushed superficially away from the stratum basale. Two other cell types are found dispersed among the basal cells in the stratum basale. The first is a Merkel cell    , which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The second is a melanocyte    , a cell that produces the pigment melanin. Melanin gives hair and skin its color, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage.

In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.

Stratum spinosum

As the name suggests, the stratum spinosum    is spiny in appearance due to the protruding cell processes that join the cells via a structure called a desmosome    . The desmosomes interlock with each other and strengthen the bond between the cells. It is interesting to note that the “spiny” nature of this layer is an artifact of the staining process. Unstained epidermis samples do not exhibit this characteristic appearance. The stratum spinosum is composed of eight to 10 layers of keratinocytes, formed as a result of cell division in the stratum basale ( [link] ). Interspersed among the keratinocytes of this layer is a type of dendritic cell called the Langerhans cell    , which functions as a macrophage by engulfing bacteria, foreign particles, and damaged cells that occur in this layer.

Questions & Answers

draw the male reproductive system
Jeremaih Reply
hello am new here
how life
Explain how different foods can affect metabolism
Abraham Reply
what is Endocrine system?
Islam Reply
which secrete hormones and other products direct into the blood
Cell is basic, structural and functional unit of life
Kabuja Reply
The cell is the structural and functional unit of all living organisms, and is sometimes called the "building block of life." Some organisms, such as bacteria, are unicellular, consisting of a single cell.
hi am new here..wish to join you in this conversation
welcome Rachel am Brianito
can some one help
what is the basic function of the lymphatic system
The other main function is that of defense in the immune system. Lymph is very similar to blood plasma: it contains lymphocytes. It also contains waste products and cellular debris together with bacteria and proteins. Associated organs composed of lymphoid tissue are the sites of lymphocyte producti
the function of lymphatic system are 1fluid balance 2 lipid absorption and 3 defence
destroyed microognism
lymphatic systems main function is to transport lymph
may i know the meaning of infestation of parasite?
Which of the following accurately describe external respirations
Robin Reply
different between anatomy and physiology
Samwel Reply
anatomy is the study of STRUCTURE of the body while physiology is the study of the function of the part of the body
Anatomy deals with the structure and parts of the body while physiology is the function of the the body parts
not understanding what is a cell
Kesa Reply
its the fundamental unit of life or its the primary step in which two or more cell combine to form a tissue .
Is the smallest structural and functional unit of life
cell is the basic you unit of life
what is osteomalàcia
Ellen Reply
what is hydroxyapitate
Hydroxyapatite, also called hydroxylapatite, is a naturally occurring mineral form of calcium apatite with the formula Ca₅(PO₄)₃, but it is usually written Ca₁₀(PO₄)₆(OH)₂ to denote that the crystal unit cell comprises two entities. Hydroxyapatite is the hydroxyl endmember of the complex apatite gro
what's the best way to memorize the terms and what it does
osteomalacia is where inorganic or mineral which is calcium and phosphorus are removed from a bone....this will make the bone become flexible n in children is called ricket
wat work does anatomy do in the hospital and can they get work fast after finishing
SULE Reply
what is the meaning of suture?
praba Reply
it is a protective layer of brain
it is a kind of non movable joint present between skull bones
suture is an example of fibrous joint and is synatrosys(is not movable)
a junction between the sclerites of an imsect's body
c organ,organ system, organism
Dorothy Reply
reproductive sytstem
describe structure and functions of spleen
Umesh Reply
why calcium does not prodecessed by biological process?
James Reply
when calcium isn't processed that becomes Calcium Homeostasis
follow this link for extra info on all processes of calcium including calcium metabolism > ***google.com/url?sa=t&source=web&rct=j&url=***opentextbc.ca/anatomyandphysiology/chapter/6-7-calcium-homeostasis-interactions-of-the-skeletal-system-and-other-organ-systems/&ved=2ahUKEwi06LTw-sP
Copy it and paste it on your browser url
What are the functions of batholine glan
Aliyu Reply
Of what
what is pathogen
Nafiw Reply
an organism who invades the susceptible host
what tenderness chord
Tenderness A She tried to show me how to love D I bit her lips and bruised ...
is not
Pathogens are decease causing agents.... it can be a viral infection or fungai infection... thank u
laws of Gregor mended of genetics
What is nosocomial
hospital accused infection.
Hospital acquired infections
Hospital acquired infections
Hospital acquired infection

Get the best Anatomy & Physiology course in your pocket!

Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?