Histology Lec 1 Intergumentary

an epithelial epidermis and a connective tissue dermis, which in turn is attached to a subcutaneous areolar/adipose hypodermis, also known in gross anatomy as the superficial fascia

from ectoderm.

exocrine

alveolar (a.k.a. "acinar") or tubulo-alveolar (a.k.a. "tubulo-acinar")

the stratum germinativum (a.k.a. stratum basale); the fairly thick stratum spinosum; the stratum granulosum with the keratohyalin granules; the translucent stratum lucidum; and the scale-like stratum corneum.

Meissner's Corpuscle.

eumelanin (as opposed to phaeomelanin) granules produced by melanocytes that are present in the basal layer of the epidermis

In strata basale and spinosum by ultraviolet
irradiation of 7-dehydrocholesterol

Epidermis
Dermis
Hypodermis
(Superficial fascia)

Stratified squamous
epithelium with four (thin
skin) or five (thick skin)
distinctive strata
• Avascular

Papillary dermis
Reticular dermis

Loose irregular
connective tissue

Dense irregular
connective tissue

• Loose irregular
connective tissue

Stratum corneum
• Stratum lucidum
– present only in
thick skin
• Stratum
granulosum
• Stratum spinosum
• Stratum basale
(germinativum)

A single cell
layer that resides
on top of the
basement
membrane
• Contains
epidermal stem
cells.
• Contains
melanin

Hemidesmosomes and Desmosomes in the focal adhesion

• Spinous cells have
spine-like
cytoplasmic
extensions
• Desmosomal
adhesions

Contains
keratohyalin
granules.
• Contains lamella
bodies

• Present only in
thick skin
• Thin clear layer of
dead cells in
between stratum
granulosum and
stratum corneum
• Devoid of nuclei

• Devoid of cellular
organelles and
nuclei
• Contain tonofibrils
(keratin fibrils)
• Create a physical
barrier to protect
layers beneath.
• Apical layers are
desquamated

Keratinocytes
Melanocytes
Merkel cells
Langerhans cells

The majority of epidermal cells

Produce melanin
• Reside in the stratum basale

Constitute a mechanoreceptor

Epidermal dendritic cells
• Reside in the stratum spinosum
• Antigen presenting cells

Corneum cells
Lucidum cells
Granular cells
Spinous cells
Basal cells

pH-dependent
activation of
KLK (Kallikrein) leads to
desmosome
degradation at
apical layers of
epidermis,
which causes
desquamation. The ph change inactivates the Lymphoepithelial Kazal type inhibitor, KLK is no longer inhibited as a result.

Cell envelope
Lipid Envelope

Involucrin protein is deposited into the cell membrane. Loricirin is also deposited in the membrane and it cross links with invoulcrin. Granular cells release kerathohyalin granules containing fillagrin and trichohyalin. Fillaggrin helps in the aggregation of keratin fibrills

Lamellar body inside granullar cell released into intracellular space.

Reside in the
stratum basale.
• Melanin-
(melanosome)
producing cells
• Thymidine
dinucleotides
from damaged
DNA will trigger
melanogenesis.

neighboring keratinocytes.

the
tone of skin clolor.

BRAF
mutation, which
can be targeted
by a specific
inhibitor.

Neurosecretory
granules+, Keratin+
– Probably of
epidermal origin

synapse-like
contacts with
enlarged terminal
endings of
myelinated nerve
fibers "Mechanoreceptor"

Bone marrow derived
• Reside in the stratum
spinosum
• Clear cells in the stratum
spinosum stained with
H&E
• Professional antigen
presenting cells
– MHC class II positive
– Motile
• Positive for CD1a, S100
etc.

Loose irregular
connective tissue
– Capillary vessels
– Meissner's corpuscles

Dense irregular
connective tissue
– Blood vessels
– Sweat glands

Adipose tissues
• Loose connective
tissues
• Pacinian corpuscles
• Blood vessels
• Sweat glands
• Hair follicle roots
(thin skin)

Low frequency stimuli

Pressure and vibration

The subpapillary plexus, cutaneous plexus, subcutaneous plexus.

Hair follicles
• Sweat glands
• Nail

Arrector pili
muscle
• Follicular bulb
• Hair bulb
• Hair papilla
• Sebaceous
glands
• Apocrine sweat
glands

sympathetic
branch of the
autonomic
nervous system

epidermal stem cells

apocrine secretion and the milk protein casein by merocrine secretion

Excrete sebum to
the infundibulum
via holocrine
mechanism.

The secretory vesicle approaches the apical domain of an epithelial cell. The vesicular membrane fuses with the plasma membrane to release its contents into the extracellular space. The fused plasma membrane can be taken back into the cell by endocytosis and recycled for further use by secretory vesicles

some of the apical cytoplasm is pinched off with the contained secretions

the cell produces and accumulates a secretory product in the cytoplasm, such as sebum in sebaceous glands and then it desintegrates to release the secretory material

-Located throughout
skin, both thick and
thin
-Merocrine secretion
watery, smaller lumen
diameter
-Clear cells produce
water & ions and dark
cells the protein
-NaCl reabsorbed in
the excretory duct

Located in axilla, anal
region & mons pubis
• Larger diameter lumen
than eccrine glands
• Merocrine secretion
viscous, activity starts
at puberty
• One cell type
secretes, secretion
not modified in duct
• Pheromones

Contain
glycoproteins
– Produce
proteinaceous
secretion

Contain glycogen
– Produce watery
components of sweat
• Myoepithelial cells
– Help excrete sweat

epithelial linings in GI & respiratory tracts and
in exocrine glands, eccrine sweat & pancreas;
decreased reabsorption of Cl ion in the duct
results in increase NaCl in the sweat

hard
keratin, which
corresponds to the
stratum corneum

nail
matrix, where
keratinocytes
proliferate, make
hard keratin and die

Fibrin clot forms,
neutrophils move in,
surface dries (i.e.,
scab)
• Macrophages remove
debris, granulation
tissue fills space
• Reepithelization by
keratinocytes
• Collagen deposition &
scar formation by
fibroblasts