Lecture #1 & 2
Integumentery System and its Appendages
This system consists on skin and its derivatives include Hair, Hoof, Skin
Glands etc. Skin is a Latin word meaning cover. It is the largest and heaviest organ,
accounting for about 16 percent of total body weight. It is thickest at dorsal surface of the
body and thinnest at the ventral surface of the body.
Function:
It is a barrier against environment, microorganism and helps to maintain
internal body temperature (thermoregulation). The skin consists on two layers Epidermis
and Dermis. Skin
1. EPIDERMIS
Epidermis is derived from ectoderm and outer most layer of skin. It consists
on two cell types, which includes keratinocytes and nonkeratinocytes (melanocytes,
langerhans and Merkels cells). The keratinocytes cells are keratinized stratified
squamous epithelium. These keratinocytes cells involves in the process of renewal of
skin surface, which involoves four overlapping stages: cell renewal (mitosis), cell
differentiation (keratinization), cell death (apoptosis) and the sloughing of dead cells
from the surface (exofoliation).
Nonkeratinocytes Cells
a) Melanocytes:
There cells are present in basal layer of Epidermis. The melanocytes has a
spherical nucleus and cytoplasm contain ovoid granules are known as melanosomes,
which is responsible for colour of skin and hair. The dark brown pigment in skin is called
eumelanim, white yellowish, red pigment is called pheomelanim.
b) Tactile Epithelioid Cells (Merkel Cells)
ANAT-104 Systematic Veterinary Histology & Embryology Dr. Nisar Ahmed
, Located in basal region of the epidermis of both hair less and hairy skin. The
nucleus is lobulated irregular and cytoplasm is clear. These cell secrete some substance
like, serotonin, polypeptide, peptide etc.
c) Intraepidermal Macrophages (Langerhans cells)
Located in the spinous layer of epidermis. The cytoplasm contains rod
shaped or racket-shaped granules and has immense response to perform phagocyte
system.
Layers of Epidermis
1. Startum Basale
It consists on a single layer of columnar or cuboidal epithelium rest on the
basal lamina some basal cells act as stem cells divide and produce new cells. it is
innermost layer of epidermis and directly connected with dermis.
2. Stratum Spinosum (Prickle cell Layer)
It consists on several layers of cuboidal or polygonal cells, cytoplasm
contains tonofilament.
3. Stratum Granulosum
It is third layer, which consists on five layers of flattened cells lying parallel
to the epidermal junction. This layer contain keratohyalin granules, they syntheses
filaggrin and secrete glycosaminoglycon and phospholipid into the intercellular spaces,
which act as a intercellular cement.
4. Stratum Lucidum
It is clear layer and only found in specific areas of exceptionally thick skin
and in hair less region. Consists on fully keratinized, closely compacted dense cells.
5. Stratum Corneum
It is outer most layer of epidermis and consists on several layers of
completely keratinized dead cells, plate-like enucleate with thickened plasma membrane,
which are constantly being shade.
ANAT-104 Systematic Veterinary Histology & Embryology Dr. Nisar Ahmed
Integumentery System and its Appendages
This system consists on skin and its derivatives include Hair, Hoof, Skin
Glands etc. Skin is a Latin word meaning cover. It is the largest and heaviest organ,
accounting for about 16 percent of total body weight. It is thickest at dorsal surface of the
body and thinnest at the ventral surface of the body.
Function:
It is a barrier against environment, microorganism and helps to maintain
internal body temperature (thermoregulation). The skin consists on two layers Epidermis
and Dermis. Skin
1. EPIDERMIS
Epidermis is derived from ectoderm and outer most layer of skin. It consists
on two cell types, which includes keratinocytes and nonkeratinocytes (melanocytes,
langerhans and Merkels cells). The keratinocytes cells are keratinized stratified
squamous epithelium. These keratinocytes cells involves in the process of renewal of
skin surface, which involoves four overlapping stages: cell renewal (mitosis), cell
differentiation (keratinization), cell death (apoptosis) and the sloughing of dead cells
from the surface (exofoliation).
Nonkeratinocytes Cells
a) Melanocytes:
There cells are present in basal layer of Epidermis. The melanocytes has a
spherical nucleus and cytoplasm contain ovoid granules are known as melanosomes,
which is responsible for colour of skin and hair. The dark brown pigment in skin is called
eumelanim, white yellowish, red pigment is called pheomelanim.
b) Tactile Epithelioid Cells (Merkel Cells)
ANAT-104 Systematic Veterinary Histology & Embryology Dr. Nisar Ahmed
, Located in basal region of the epidermis of both hair less and hairy skin. The
nucleus is lobulated irregular and cytoplasm is clear. These cell secrete some substance
like, serotonin, polypeptide, peptide etc.
c) Intraepidermal Macrophages (Langerhans cells)
Located in the spinous layer of epidermis. The cytoplasm contains rod
shaped or racket-shaped granules and has immense response to perform phagocyte
system.
Layers of Epidermis
1. Startum Basale
It consists on a single layer of columnar or cuboidal epithelium rest on the
basal lamina some basal cells act as stem cells divide and produce new cells. it is
innermost layer of epidermis and directly connected with dermis.
2. Stratum Spinosum (Prickle cell Layer)
It consists on several layers of cuboidal or polygonal cells, cytoplasm
contains tonofilament.
3. Stratum Granulosum
It is third layer, which consists on five layers of flattened cells lying parallel
to the epidermal junction. This layer contain keratohyalin granules, they syntheses
filaggrin and secrete glycosaminoglycon and phospholipid into the intercellular spaces,
which act as a intercellular cement.
4. Stratum Lucidum
It is clear layer and only found in specific areas of exceptionally thick skin
and in hair less region. Consists on fully keratinized, closely compacted dense cells.
5. Stratum Corneum
It is outer most layer of epidermis and consists on several layers of
completely keratinized dead cells, plate-like enucleate with thickened plasma membrane,
which are constantly being shade.
ANAT-104 Systematic Veterinary Histology & Embryology Dr. Nisar Ahmed
