Foundations - Histology Epithelia and Skin

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Introduction

Skin and appendages
Stratified epithelia
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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.


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

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.

Epithelia

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

Epithelium histology cartoon 01.jpg Epithelium histology cartoon 02.jpg
Epithelia cell shape Epithelia sectioning appearance

Epithelia Classification

  1. The number of cell layers: a single layer = simple epithelium; epithelia composed of more than one layer = stratified epithelia.
  2. 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).
  3. The presence of surface specializations e.g. cilia, microvilli and keratin.

Simple Epithelium

Simple Squamous

Virtual slides: Distributing artery and vein and Aorta

Vein histology 01.jpg

Vein simple squamous epithelium. (Stain - Haematoxylin Eosin)


Simple Cuboidal

Virtual slides: Thyroid gland and Kidney

Thyroid histology 002.jpg Nephron histology 04.jpg
Thyroid follicles Renal tubules

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


Simple Columnar

Virtual slides: Fallopian tube-isthmus and Duodenum

Duodenum histology 01.jpg

Duodenum (Stain - Haematoxylin Eosin)

Ileum histology 01.jpg

Ileum (Stain - Haematoxylin Eosin)

Stratified Epithelium

Stratified Squamous Non-Keratinising

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

Oesophagus histology 04.jpg Oesophagus histology 05.jpg

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 histology stratified columnar 01.jpg

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 histology 01.jpg

Epididymis

Trachea histology 01.jpg

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)

Bladder histology 01.jpg

Skin

Virtual slide: Thick skin (human palm).

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


Histology

Adult skin histology 02.jpg

Skin overview (Stain - Haematoxylin Eosin)

Adult skin histology 03.jpg

Skin overview (trichrome stain)

Adult epidermis histology 01.jpg

Epidermis (thin skin)

Adult epidermis histology 02.jpg

Epidermis (thick skin)

Adult skin histology 01.jpg

Epidermis and Dermis

Integumentary- hair follicle 01.jpg

Hair follicle

Pigmentation

Adult epidermis histology 03.jpg

Melanin in Basal Cell Layer

Glands and Hair

Gland Secretion Mechanisms

Merocrine secretion animation.gif Apocrine secretion animation.gif Holocrine secretion animation.gif
Merocrine secretion Apocrine secretion Holocrine secretion

Sensory

Touch Pressure
Meissner corpuscle 01.jpg Pacinian corpuscle histology 01.jpg
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.


Integument Histology Links: Adult Skin | Epidermis and Dermis | Thin Skin Epidermis | Thick Skin Epidermis | Basal Cell Melanin | Foundations Practical Support | Integumentary System Development | Histology Stains


Links: Integumentary System Development


Additional Information - Keratinocyte Development

Epidermis cartoon 01.jpg

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.

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.
  • 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.

External Links

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Cite this page: Hill, M.A. (2014) Embryology Foundations - Histology Epithelia and Skin. Retrieved July 25, 2014, from //php.med.unsw.edu.au/embryology/index.php?title=Foundations_-_Histology_Epithelia_and_Skin

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Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G