Histology Slide of a Thin Skin of an Animal
Welcome again. Hope you are fine. Today, I will discuss the thin skin of an animal (identification of skin under a microscope). Okay, before starting, you should have a basic idea about the STRUCTURE OF CELL, LINING EPITHELIUM, and CONNECTIVE TISSUE. If you don’t have basic knowledge about those topics, you may go through those links.
Histology slide of a thin skin of an animal
You know, skin is the largest organ of animal’s body. We will discuss the following structures of a histology slide of the thin skin of an animal –
The epidermis layer of skin
Under epidermis, we will identify the following structures (if possible) –
Different layers or lining epithelium of epidermis (stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum)
Cells of the epidermis (keratinocytes, melanocytes, Langerhans cells, Merkel’s cells)
Dermo-epidermal junction
We will identify the following structure –
Epidermal ridge
Dermal ridge
The dermis layer of the skin
We will identify the following structures from the dermis layer of skin (if possible) –
Papillary layer
Reticular layer
Hair follicles
Sebaceous glands
Sweat glands
Arrector pili muscle
At last, I will also discuss the layers of retina histology (identification of different layers of retina histology of animals)
Histology of skin diagram
Okay, let’s start to learn the histology of the skin diagram. I will identify the important structures from the histology slide of the thin skin of the animal.
In thin skin, you will find the thin epidermis lined by the keratinized stratified squamous epithelium. It consists of five layers and four different types of cells (I will discuss it later)
Presence of dermo-epidermal junction. A projection from the epidermis into the dermis is called the epidermal ridge; again, the projection from the dermis into the epidermis is called the dermal ridge.
The dermis layer is made by vascular connective tissue divided into the papillary (superficially) and reticular (deeply) layers.
The papillary layer is thinner and consists of loose connective tissue and protrudes into the dermis from dermal papillae.
Again, the reticular layer is thicker and dense irregular collagenous connective tissue. Here, you will find the sebaceous and sweat gland (you need to differentiate sebaceous gland from sweat gland; Okay, I will discuss it later)
You will find a smooth muscle fiber near the hair follicles called arrector pili muscle.
You will also find more blood and lymph vessels in the skin’s reticular layer.
Okay, now I will discuss five different layers of histology of skin diagram and also about sebaceous and sweat glands of animal’s skin. Okay, let’s start –
Epidermis layers of skin
You will find five epidermis layers of skin of an animal (keratinized stratified squamous epithelium). They are as –
Stratum basale
Consists of a single layer of columnar or cuboidal cells that rest on the basal lamina. The nuclei of those cells are larger ovoid. You will also find melanocytes and Merkel cells in this layer.
Stratum spinosum
This layer is also called the prickle cell layer of skin. You will find several layers of polyhedral cells with a large oval nucleus. You will find tonofilaments in the cytoplasm of those cells (this is the most important feature to identify this cells layer). You will also find Langerhans cells in this layer.
“Stratum basale and stratum spinosum are called stratum Malpighi or malpighian layer as all kitotic activity of epidermis layer occur in this region.”
Stratum granulosum
You will find several layers of flattened polygonal or diamond-shaped cells that contain lamellar granules in their cytoplasm.
This layer acts as a waterproof barrier, releasing lipid content by exocytosis.
Stratum lucidum
It is a thin, translucent, homogenous line between the stratum granulosa and stratum corneum layer of skin. But, in a thin skin, it is absent. You will find this layer in thick skin only.
Stratum corneum
It is more than the supper layer of the epidermis. You will find several layers of completely dead cells (keratin substance).
“You should know the overall functions of skin or specific functions of different layers of epidermis and dermis. So, you need to follow class lectures or go through the books for details.”
Now, I am going to discuss different layers of retina histology.
Layers of retina histology
The retina is the innermost part of the eyeball. It would be best if you studied more on the retina. Here, I will discuss the most important histology of layers of the retina.
First, we should know the following layers of the retina of animals –
Pigment epithelium layer
A layer of rods and cones
External limiting membrane
Outer nuclear layer
Outer plexiform layer
Inner nuclear layer
Inner plexiform layer
Ganglion cell layer
Optic nerve fiber layer and
Internal limiting membrane
In the pigment epithelium layer, it is formed by simple squamous or cuboidal epithelium resting on a basal lamina. Those cells have numerous melanin granules in their cytoplasm and several layers of leaf-like process at the apical portion.
A layer of rods and cones is a photoreceptor layer and consists of the outer segment of rods and cones and the inner segment of rods and cones connected by cilium or cilia.
The external limiting membrane is a junction between radial glia and photoreceptor cells.
The outer nuclear layer is consists of cell bodies of rods and cones cells
An outer plexiform layer is formed by the synapses of axon fibers of rods and cones cells with the dendrite of bipolar neurons and horizontal cells.
An inner nuclear layer is formed mainly by cell bodies of bipolar neurons and also by horizontal cells.
The inner plexiform layer is the region of synaptic contact between bipolar and ganglionic cells, between amacrine and ganglionic cells, or between adjacent amacrine cells.
The ganglionic cell layer is consists of large multipolar neurons with large euchromatic nuclei.
The axon of ganglionic cells forms the nerve fiber layer
The internal limiting membrane layer is formed by the expanded process of radial glial cells.
“You need to differentiate rods cells from cone cells.”
Conclusion
I hope you have got an idea of the histology slide of a thin skin of an animal (histology of skin diagram). You may also learn the basic histology of the organs from the DIFFERENT SYSTEM OF ANIMAL BODY. If you want to know more about the histology of the histology slide of thin skin and thick skin, you should follow class lectures or go through the BOOKS. And I also recommended learning more on layers of retina histology from class lectures or books.
If possible, I will update or enrich the information on this topic in the future.
Again, if there is any mistake in the above information or if you have any suggestions for me, please, let me know in the comment box. Thank you so much.