Histology of Integumentary and Musculoskeletal Systems PDF

Y1B4M1L2 MUSCULOSKELETAL / INTEGUMENTARY SYSTEMS LECTURER DR. M.I. SALAZAR OCTOBER 17, 2023 | 8 00 - 12 00 HISTOLOGY OF INTEGUMENTARY AND MUSCULOSKELETAL SYSTEMS TABLE OF CONTENTS I. Integumentary System A. Composition B. Function II. Skin Layers A. Epidermis 1. Stratum Corneum 2. Stratum Lucidum...

Y1B4M1L2 MUSCULOSKELETAL / INTEGUMENTARY SYSTEMS LECTURER DR. M.I. SALAZAR OCTOBER 17, 2023 | 8 00 - 12 00 HISTOLOGY OF INTEGUMENTARY AND MUSCULOSKELETAL SYSTEMS TABLE OF CONTENTS I. Integumentary System A. Composition B. Function II. Skin Layers A. Epidermis 1. Stratum Corneum 2. Stratum Lucidum 3. Stratum Granulosum 4. Stratum Spinosum 5. Stratum Basale B. Dermis C. Hypodermis III. Appendages of the Skin A. Hair B. Nails C. Sebaceous Glands D. Sweat Glands IV. Muscles A. Skeletal Muscle B. Cardiac Muscle C. Smooth Muscle D. Muscle Contraction Summary V. Bones A. Macroscopic Structures 1. Compact bone 2. Spongy bone B. Microscopic Structures 1. Cells of bone C. Bone Matrix 1. Collagen 2. Bone Mineral VI. Summary VII. Review Questions VIII. References IX. Appendices radiation. At the same time, sweat glands secret more sweat that cools the body when it evaporates. ● Provide sensations ○ It contains millions of nerve endings that act as sensory receptors for pain, heat, cold, and pressure ○ When stimulation occurs, nerve impulses are sent to the cerebral cortex of the brain and the brain triggers any necessary response II. SKIN LAYERS ● Two layers: ○ Epidermis → Thin skin (elsewhere in the body) = 4 layers (absence of stratum lucidum) → Thick skin (on the palms and soles) = 5 layers ○ Dermis or corium I. INTEGUMENTARY SYSTEM A. COMPOSITION ● Skin – largest organ of the body 16% of body weight). It is supplied with blood vessels and nerves. ● Accessory structures: ○ Hair ○ Nails ○ Sebaceous glands ○ Sweat glands ● Two layers: ○ Epidermis - has 4 or 5 layers of strata → Down growths: interpapillary pegs or rete pegs ○ Dermis → Projections: dermal papillae Figure 1. Layers of the Skin ● There are also three less abundant epidermal cell types: ○ pigment-producing melanocytes ○ antigen-presenting Langerhans cells ○ tactile epithelial cells called Merkel cells ● Varies in thickness from 0.07 to 0.12 nm B. FUNCTIONS ● Skin provides protection ○ Protects against invasion by bacteria and other harmful agents ● Protects delicate cells beneath the surface from injury ● Inhibits excessive loss of water and electrolytes ● Produces a protective pigmentation to protect the body against excessive exposure from the sun ○ Medium to dark colored people are protected against injury ○ Less risk factor for the development of malignancy ● Helps produce the bodyʼs supply of Vitamin D ● Regulates body temperature ○ When the body is too cold skinʼs blood vessels constrict → This allows more heat-carrying blood to circulate to the muscle and organs. ○ When the body is too hot, the blood vessels in the skin dilate. That brings more blood to the surface for cooling by Figure 2. Histological Layers of the Skin AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 1 of 26 Y1B4M1L2 HISTOLOGY OF INTEGUMENTARY & MUSCULOSKELETAL SYSTEMS A. EPIDERMIS ● Consists mainly of a stratified squamous keratinized epithelium composed of cells called keratinocytes ○ Only squamous cells can produce keratin, thus they are also called keratinocytes ● Layers of Epidermis: ○ Stratum corneum ○ Stratum lucidum ○ Stratum granulosum ○ Stratum spinosum ○ Stratum basale/ germinativum Figure 5. Layers of Epidermis, a (histo high magnification showing the skin) Figure 3. Histological Layers of the Skin Figure 6. Layers of Epidermis, b (histo) STRATUM CORNEUM ● Most superficial or outermost layer of the epidermis ● It is mostly dead cells, filled with a protein substance called keratin ● It is thicker on the soles of the feet than on the eyelids Nice-to-Knows/Additional Information: ● Lifeless cells loosen and ultimately desquamate are found on outer layers and are sometimes called stratum disjunction ● As keratinocytes ascend through the several strata, they enlarge and become more flattened ● Protects against friction and water loss Figure 4. Layers of the Epidermis Lecture Notes: ● Keratin - helps in protection and aids in fluid loss ● Melanocytes - located on the base; alternating with the keratinocytes ○ Dermal and epidermal junction significance: melanoma, melanocytes are present in this layer ● Tumors can arise from melanin and keratin ○ Tumors can arise from keratinocytes – squamous cell carcinoma; can be in situ ● Pigmentation - high risk form malignancies ○ Moles (nunal) or nevus cells arise from the the basal membrane, proliferate in the dermis ● Stratum corneum - mostly dead cells; abundance of keratins ● Granulosum - no stratum lucidum; cytoplasm ● Stratum spinosum - has Intercellular bridges - significant; not seen in other epithelial cells (transitional cells/urothelial) ● Transitional - found mostly in genitalia (tract); urothelium Figure 7. Stratum Corneum STRATUM LUCIDUM ● Translucent layer lying directly beneath the corneum ○ Found only in thick skin ● Cells in this layer are also dead or are in the process of dying AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 2 of 26 Y1B4M1L2 HISTOLOGY OF INTEGUMENTARY & MUSCULOSKELETAL SYSTEMS Figure 8. Stratum Lucidum Figure 9. Stratum Granulosum Nice-to-Knows/Additional Information: ● Consists of four to six rows of very flat cells and is usually not identifiable in thinner skin of other regions ● Nuclei are rarely seen because it began to degenerate in stratum granulosum ● Keratin filaments are closely aggregated and are more consistent in their parallel orientation to the skin surface ● Cell membrane appears thickened by deposition of dense materials in the inner surface ● It appears as a pale, wavy stripe, with refractile droplets called eleidin instead of keratohyalin granules STRATUM SPINOSUM STRATUM GRANULOSUM ● One or more layers of cells start to die and become hard ○ In the process of keratinization becoming fibrous protein similar to that in hair and nails ● More flattened than stratum spinosum ● Distinguishing feature: ○ Presence of bodies of large size ○ Irregular shape that stain intensely with basic dyes ● Contains keratohyalin granules that do not have a limiting membrane and are believed to be precursors of an interfibrillar matrix which is distributed throughout the cytoplasm of fully keratinized cells ● Presence of more lamellar granules than in stratum spinosum which occupies as much as 15% of the cytoplasmic volume Clinical Correlates ● Both benign and malignant tumors can arise from most types of epithelial cells. ● Benign tumors derived from glandular epithelial tissue are called adenomas. ● Malignant tumors of epithelial origin are called carcinomas Gr. karkinos, cancer + oma, tumor). ● Malignant tumors derived from glandular epithelial tissue are called adenocarcinomas Gr. adenos, gland + karkinos). Adenocarcinomas are by far the most common tumors in adults after age 45. ● Clark Levels ○ The Clark Level is a staging system that describes the depth of melanoma as it grows in the skin. ○ Depth of invasion is directly proportional to the stage of cancer. ● Also known as Stratum Malphigii ● With less intensely basophilic cytoplasm than the stratum basale ● Prominent feature: ○ Presence of numerous bundles of cytokeratin intermediate filaments that radiate from the perinuclear region and end in the dense plague of numerous desmosomes along highly interdigitated cell boundaries ● Cytoplasm has secretory granules called membrane-coating granule or lamellar granules which have a limiting membrane and a distinctive internal structure consist of closely packed parallel lamellae. STRATUM BASALE GERMINATIVUM ● Composed of several layers of living cells capable of cell division ● Innermost layer of the epidermis ● Contains melanin ○ The pigment that gives color to the skin ○ The more abundant the melanin, the darker the skin color ● Damage to this layer, such as severe (third degree) burns, requires skin grafts Figure 10. Stratum Germinativum AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 3 of 26 Y1B4M1L2 HISTOLOGY OF INTEGUMENTARY & MUSCULOSKELETAL SYSTEMS ● Stratum basale was formerly Stratum Germinativum ● Single layer of cells supported by basal lamina resting on the dermis ● Cells are cuboidal or low columnar ● With a large nucleus and basophilic cytoplasm BASAL LAMINA ● Formerly called basement membrane ● Consists of lamina densa parallel to the membrane of basal cells of the epithelium ● Separated from the membrane of basal cells by thin lamina lucida, which is traversed by exceedingly thin filaments crossing from the cell membrane to the lamina densa ● With anchoring fibrils that extend downward, arch around collagen bundles in the dermis, and terminate in anchoring plaques (small bodies with same density and substructure as lamina densa) LAMINA DENSA ● Fine meshwork of Type IV collagen and contains heparan sulfate and glycoproteins Figure 12. Melanocytes with brown black melanin pigment LANGERHANS CELLS ● Similar to macrophages ● Have affinity for catecholamines and L DOPA ● Most numerous in the epidermis but are occasionally found in the dermis ● Participate in bodyʼs immune responses ○ Equivalent of lymphocytes ● Isolated dendritic cells that are usually located in the upper layers of the stratum spinosum ANCHORING FIBRILS ● Believed to bind epithelium firmly to the dermis ● Have beaded, cross – striated appearance of Type VII collagen CELLS FOUND IN EPIDERMIS ● Melanocytes ● Langerhans Cells ● Merkel Cells Figure 13. Cells in the Epidermis ● MELANOCYTES ● Color of the skin is the result of several factors: keratinocytesʼ content of melanin and carotene and the number of blood vessels in the dermis ● Produce the skin pigment melanin because of the presence of tyrosinase ○ Eumelanins - brown or black pigments produced by the melanocyte ○ Pheomelanin – pigment found in red hair ● Melanin are incorporated in the cytoplasmic granules or melanosomes of melanocytes and also in the keratinocytes or epidermal squamous cells Lecture Notes: ● Melanosome - releases the pigments ● Surface - ground black pigment - dark skin color ● Keratinocytes - same with squamous cells ● For every 8 10 keratinocytes - there is 1 melanocyte ● Brown black pigment - melanocyte Figure 11. Melanocytes ● ● ● ● ● With dark, staining nucleus and pale, clear cytoplasm in a routine hematoxylin and eosin preparations Most reliable feature: ○ Presence of Birbeck granules (vermiform granules) → Which are unique membranes → Limited granules → Have a discoid three-dimensional form → Has no enzymatic activity Possess surface receptors and immunological markers Carry T 4 antigens on their surface like T–lymphocytes Important agents in contact allergic responses and other cell–mediated immune reactions of the skin Come from a pool of precursors in the bone marrow MERKEL CELLS ● Found in the basal layers of the epidermis which are more abundant in fingertips (role in sensory perception) ● Forms Meckel cell – neurite complexes with the naked terminals of myelinated afferent nerves in the basal lamina ● Bear a superficial resemblance to keratinocytes to which they may be attached by desmosomes ● Nucleus deeply invaginated and may contain a strange inclusion consisting of a bundle of short parallel filaments ● Cytoplasm has low electron density and contains loose bundles of cytoskeletal filaments in perinuclear region and at cell periphery ● Contains cytokeratins K8, K18, and K19 ● Presence of many dense–cored granules in the perinuclear cytoplasm and in dendritic–like processes ● Have a role in paracrine regulation of neighboring epidermal components like the neuroendocrine cells of GI and bronchopulmonary epithelia AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 4 of 26 Y1B4M1L2 HISTOLOGY OF INTEGUMENTARY & MUSCULOSKELETAL SYSTEMS ● Origins: ○ Derivatives of neural crest ○ Differentiated in the epidermis from cells of the stratum germinativum MUCOCUTANEOUS JUNCTION ● Transitions from the skin to the mucous membrane lining the orifices of the body (e.g. mouth, anus) ● Stratified squamous epithelium ● Closely resemble mucosa than skin ● Very thin stratum corneum ● Color of blood in underlying capillary bed shows through, gives red tint ● No hairs, sebaceous gland, sweat gland ● Surface is moistened by mucous glands products B. DERMIS CORIUM ● Located below epidermis and is composed of connective tissues ● Sebaceous gland ○ Found in the upper part of the dermis ○ Papillary layer - ridges unique fingerprints and footprints ○ Secretes oil and nourishes the hair follicles → Unique fingerprints Figure 15. Epidermis and Dermis Figure 16. Dermis LAYERS OF THE DERMIS PAPILLARY LAYER Figure 14. The Dermis ● Contains: ○ Lymphatics ○ Nerves ○ Nerve endings ○ Blood vessels ○ Sebaceous and sweat glands ○ Elastic fibers ○ Hair follicles ● Composed of tough leathery layer of connective tissue ● Makes for the thickness of skin ● Thickness ranges from 0.6 mm (in eyelids) to 3 mm (in palm & sole) ● Average = about 2mm ● Thinner in ventral surface of body and extremities ● Thinner on women ● Primary ridges – ridges forming dermatoglyphic pattern on skin surface ○ Dermal papillae rows projects upward from these ridges ● Dermis has rich vascular bed to supply nutrients ● Arranged into microscopic structures that form ridges ○ These are the fingers and footprints ● Consists of fibroblast, elastic fibers, and capillaries ● Mainly Type III collagen RETICULAR LAYER ● ● ● ● Deeper, beneath the papillary layer White fibrous tissue that supports the blood vessels Consist of dense irregular connective fibers of Type I collagen Arrector pili muscles contraction in the reticular layers is responsible for the “goose-flesh” when exposed to cold environment ○ Connective tissue fibers → Dense irregular tissue in the skin (oriented on different angles) ○ Skinʼs connective tissue is not that oriented (Type I collagen) ○ Collagen in dermal → Not oriented in one direction AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 5 of 26 Y1B4M1L2 HISTOLOGY OF INTEGUMENTARY & MUSCULOSKELETAL SYSTEMS Figure 19. The Hypodermis Figure 17. Papillary and Reticular Layers ● Made up of closely packed coarse bundles of thicker fibers Dense Irregular Connective Fibers) ● Dominantly Type I Collagen ○ Oriented parallel to the skin surface, some may run obliquely or perpendicular to the majority ● Network of elastic fibers are abundant around sebaceous and sweat glands ● Space between fibers are occupied with proteoglycan ○ Main component: Dermatan sulfate ● Arrector pili muscles ○ Insert into the body of hair follicles ● Muscles of Facial Expression ○ Cross-striated muscles fibers terminating in the dermis of face, scalp, base of the ear ● Important to know the depth of invasion of tumors in the skin ● Subcutaneous layer deep to the reticular, composed of adipose and connective tissue ● Looser connective tissue ● Thin collagen fibers are parallel to skin surface ● Supports, nourishes, insulates, and cushion the skin ● Panniculus adiposus ○ Layer of fat in abdomen, thigh, and buttocks 3 cm or more) III. APPENDAGES OF THE SKIN SKIN ADNEXA A. HAIR ● Threadlike structure formed by a group of cells that develop within a hair follicle or socket ● Each hair has a shaft that is visible and a root that is embedded in the follicle ● Arrector pili muscle / Pilomotor muscle ○ Small bundle of smooth muscle cells ○ Originates from the papillary layer of the dermis ○ Inserts into the connective sheath of the hair follicle slightly above its midpoint ○ Its contraction pulls the hair shafts to a more erect position in an effort to trap warm air ○ Attached to the side of each follicle ○ Stimulated by skin irritants, emotional arousal, or cold temperatures, and reacts by contracting ○ Causes goose flesh or goose pimples ● Hair shaft ○ Protects the inner follicle ○ Part of a hair extending beyond the skin surface Figure 18. Layers of Dermis C. HYPODERMIS ● The dermis is connected to underlying tissue by the subcutaneous tissue ● Loose connective tissue ● It supports, nourishes, insulates, and cushions the skin ● Composed of: ○ Adipose Fat Layers) ○ Connective tissue Figure 20. Arrector Pili Muscle AGULAN, ARENGA, BOLAÑO, DUARTE, FRANCISCO, NACIONALES, PIONELO, SEÑALISTA, TRESPECES, VIAJE | MG 9 6 of 26