Foundations - Histology Epithelia and Skin

Introduction

Skin and appendages

Stratified epithelia

Background and Self-directed Learning for Medicine Foundations.

Practical - Histology Epithelia and Skin Virtual Slides by Patrick de Permentier.

This current page content is not part of the Foundations practical class.

Note - In Moodle on the virtual slide page the link to Trachea is currently not available.

Use this link - Virtual Slide - Trachea

2016 Prac 9 Histology of Epithelia and Skin

Links: Histology Introduction | Histology Epithelia and Skin | Histology Stains | ANAT2241 Integumentary System | Histology Drawings

Moodle Lab Slides

Note - Moodle icon links appearing below on this page go directly to Lab Slide.
(you must be logged in to Moodle) I will be adding links to annotated slides after today's practical.

Objectives

Epithelia

Obtain an understanding of the histological appearance of various types of epithelia based on their cellular shape and number of layers.
To examine the histological appearance of 2 other unique types of epithelia namely pseudostratified and transitional.
To demonstrate some sites where the types of epithelia can be located
To demonstrate certain epithelial specialisations such as microvilli and cilia.
Relate the morphology of the epithelia to their various functions.

Skin

To know the microscopic structure of the skin e.g. epidermis, dermis and hypodermis.
To know the histological differences between hairy (thin) and glabrous (thick) skin.
To know the histology of associated structures e.g. eccrine and apocrine sweat glands, sebaceous glands, and hair.
To know the histological features of some sensory receptors namely: Pacinian and Meissner

corpuscles.

Textbooks

Wheater’s Functional Histology. A Text and Colour Atlas 6th ed. by Young, B., O’Dowd, G. and Woodford, P. (2014)

Requires student log-in

Chapter 5 - Epithelia

Chapter 9 - Skin

Epithelia

Epithelium forms continuous layers of cells that cover surfaces and line cavities of the body.


Epithelia cell shape	Epithelia sectioning appearance

Epithelia Classification

The number of cell layers: a single layer = simple epithelium; epithelia composed of more than one layer = stratified epithelia.
The shape of the component cells when seen in sections taken at right angles to the epithelial surface: the shape may be squamous (flattened), cuboidal (about equal dimensions), or columnar (taller than it is wide).
The presence of surface specializations e.g. cilia, microvilli and keratin.

Simple Epithelium

Simple Squamous

Virtual slides: Distributing artery and vein and Aorta

Vein simple squamous epithelium. (Stain - Haematoxylin Eosin)

Simple Cuboidal

Virtual slides: Thyroid gland and Kidney


Thyroid follicles	Renal tubules

Kidney - distal and collecting tubule. (Stain - Haematoxylin Eosin)

Simple Columnar

Virtual slides: Fallopian tube-isthmus and Duodenum

Duodenum (Stain - Haematoxylin Eosin)

Ileum (Stain - Haematoxylin Eosin)

Stratified Epithelium

Stratified Squamous Non-Keratinising

Virtual slides: Tongue-Foliate papillae and Cervix of uterus/vaginal canal

Stratified Squamous Keratinising

Virtual slide: Skin

See more in the Skin histology notes section below.

Stratified Cuboidal / Stratified Columnar

Virtual slides: Skin and Submandibular Gland

Parotid gland epithelium is an example of a stratified columnar epithelium.

Pseudostratified Columnar

This type is categorized as simple because all the epithelial cells make contact with the basement membrane, but not all cells reach the surface of the epithelium.

Virtual slides: Epididymis and Trachea

Epididymis

Trachea

Transitional

Located only in the urinary system, this epithelium is composed of 5 or more cell layers. Those located basally are either low columnar or cuboidal.

Virtual slides: Urinary bladder (relaxed) and Urinary bladder (partly distended)

Skin

Virtual slide: Thick skin (human palm).

Virtual slides: Thin skin (human scalp LS and TS) and Skin (axillary, human)

Histology

Skin overview (Stain - Haematoxylin Eosin)	Skin overview (trichrome stain)
Epidermis (thin skin)	Epidermis (thick skin)
Epidermis and Dermis	Hair follicle

Pigmentation

Melanin in Basal Cell Layer

Glands and Hair

Sebaceous gland histology
Sebaceous gland histology
Hair follicles
Hair follicle
Hair follicle
Hair histology

Gland Secretion Mechanisms


Merocrine secretion	Apocrine secretion	Holocrine secretion

Sensory

Touch	Pressure

Meissner corpuscle a sensory touch cellular structure located in the dermis superficial region.	Pacinian corpuscle a sensory pressure cellular structure located in the dermis deep region.

Links: Integumentary System Development

Additional Information - Keratinocyte Development

stratum corneum - keratinocytes lose their organelles, including the nucleus, and become the dead, flattened corneocytes.

stratum granulosum - keratinocytes become more flattened and express proteins that aggregate to form keratohyalin granules. Lipids are also produced and stored in lamellar bodies.

stratum spinosum - keratinocytes reinforce their cytoskeletal keratin filament network and adjacent cells interact through desmosomes.

stratum basale - (basal layer) keratinocytes proliferate by mitosis. This layer also contains the stem cell population.

Additional Information - Epithelial Specialisations

Cilia

Trachea cilia (microtubule core, motile) <html5media height="350" width="800">File:Mouse trachea 01.mp4</html5media>

Microvilli

termina web
microfilament (actin) core, immotile

Stereocilia

microfilament (actin) core, immotile

Terms

apocrine gland - (sweat gland) proteinaceous secretion associated with hair (axilla, areola, genital and anal regions). Additional glands associated with eyelashes are called the glands of Moll (ciliary gland).
arrector pili muscle - bundle of smooth muscle associated with hair follicle, inserts into the papillary layer of the dermis and attaches to the dermal sheath of the hair follicle.
bulb - the hair follicle enlargement located at its deepest end, dividing cells form the hair and the root sheath.
cilia - epithelia apical surface specialisations that are motile and move the overlying fluid. Cilia contain microtubules that are responsible for their movement, except in olfactory regions involved with smell and where they are not motile.
collagen - major filamentous protein component of extracellular matrix that add strength to the connective tissue. There are many different forms (isoforms) of collagen that have different physical properties and tissue locations.
columnar - cells are longer than they are wide.
cuboidal - cells are about the same length and width.
cutis - alternative term for the epidermis and the dermis layers of the skin.
dermis - connective tissue middle layer of the skin, consists of two sublayers (papillary and reticular layers) that do not have a clear boundary.
dermal papillae - interdigitation of the dermis with the epidermis.
epidermis - epithelial outer layer of the skin.
goblet cell - a mucus-secreting cell located in epithelia, the mucus acts as a lubricant (gastrointestinal tract) or a "trap" for particulates or organisms (respiratory). Named because their cell shape looks like a goblet, a curve-shaped cup.
hair - (pili) in humans consists of vellus and terminal hairs.
holocrine - form of gland secretion where the secretory cells eventually lyse (rupture) and are lost. On the skin these cells release sebum consisting mainly of lipid.
hypodermis - (subcutis) connective tissue inner layer of the skin that binds it to underlying structures.
integumentary - term for the skin and its appendages.
Meissner's corpuscle - sensory receptors present in the skin, touch receptors located close to the epidermis (superficial dermis region) Meissner's corpuscle image
microvilli - epithelia apical surface specialisations that increase the cell surface area, typically found in epithelia active in absorption. Microvilli contain actin filaments, which are in contact with the terminal web of the cell. The difference between microvilli (short) and stereocilia (long) is their length.
merocrine gland - (sweat gland, eccrine sweat) simple tubular glands located at the border between the dermis and hypodermis. These glands regulate the body temperature.
Pacinian corpuscle - sensory receptors present in the skin and in some mucous membranes). Mechanoceptors that respond to pressure or any mechanical stimulus deforming the corpuscle. Pacinian corpuscle image
papillary layer - dermis sublayer that appears less dense and contains more cells lying close beneath the epidermis.
rete pegs - (rete processes, rete ridges) epithelial extensions that project downward forming thickenings of the epidermis.
reticular fibres - very delicate component of extracellular matrix that form fine support network to individual cells instead of thick bundles. They are also made from a form of collagen (type III).
reticular layer - dermis sublayer that appears denser and contains fewer cells with thick collagen bundles lying parallel to the skin surface.
root sheath - cell layers that surround the hair.
sebaceous gland - holocrine gland associated with both the hair follicle and hairless parts of the skin (lips, cheek oral surface and external genitalia). Embedded in the dermis and are sites of infections (acne).
simple - consisting of a single cell layer.
squamous - flattened.
stereocilia - not cilia they are epithelia apical surface specialisations that increase the cell surface area, typically found in epithelia active in absorption. The difference between microvilli (short) and stereocilia (long) is their length.
stratified - consisting of several cell layers.
terminal hairs - hair seen in obviously hairy parts of the body.
thick skin - refers to the skin histology found on the palms of the hand and soles of the feet, do not contain hair. Note that this is used as a histological term not a measurement of overall skin thickness.
thin skin - refers to the skin histology found on skin in all other regions beside palms and soles.
vellus hairs - fine short hairs only lightly pigmented covering the body.

Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

Kierszenbaum, A. L., & Tres, L. L. (2012). Histology and cell biology: An introduction to pathology. Philadelphia, PA: Elsevier Saunders. Chapter 11. Integumentary System
Blue Histology Epithelia | Skin
UNSW Virtual Slides Medicine phase 1 (requires login for access). Histology Epithelia and Skin Virtual Slides
UIOWA Virtual Slidebox of Histology Skin

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Cite this page: Hill, M.A. (2023, December 11) Embryology Foundations - Histology Epithelia and Skin. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Foundations_-_Histology_Epithelia_and_Skin

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