Transcript sweat gland
Integument—a fancy word for skin Rachel Boggus [email protected] Skin • What are the functions of skin? (4 things) • What is considered part of the skin? (VERY GENERALLY) Skin • What are the functions of skin? – Protective barrier – Prevents desiccation of the body – Temperature regulation – Sense organ • What is considered part of the skin? (VERY GENERALLY) – Epidermis, dermis, and hypodermis (sometimes) Epidermis • What type of epithelium? • What does it give rise to? • What are the different cell types? Epidermis • What type of epithelium? – Statified squamous, keratinized • What does it give rise to? – Accessory organs—hair, nails, sweat glands (eccrine and apocrine) and sebaceous glands • What are the different cell types? – – – – Keratinocytes—most cells Melanocytes—form pigment Langerhans cells—immune reactions Merkel cells—related to specialized innervation Dermis • What does it include? • What are the two layers? Dermis • What does it include? – Collagen fibers and elastic fibers, GAGs (proteoglycans), fibroblasts, nerve endings, blood vessels, lymphatic vessels, smooth muscle • What are the two layers and their features? – Papillary layer—loose irregular CT below basement membrane – Reticular layer—dense irregular CT Back to the Epidermis • What are the 5 layers? • What is the predominant cell type that undergoes differentiation in these layers? Back to the Epidermis • What are the 5 layers? 1) 2) 3) 4) 5) • Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum What is the predominant cell type that undergoes differentiation in these layers? – The keratinocyte The changing keratinocytes • What do keratinocytes look like in the stratum basale (both LM and EM)? The changing keratinocytes • What do keratinocytes look like in the stratum basale (both LM and EM)? – LM—single basal layer—cells cuboidal columnar and basophilic • Sometimes undergoing mitosiskeratinocytes for other strata – EM—keratin filaments abundant in the cytoplasm, also have many free ribosomes Nice LM of the stratum basale Stratum Spinosum • Describe this layer in the EM and LM? Stratum Spinosum • Describe this layer in the EM and LM? – LM—cells become polygonal and flattened, several cells thick with lots of intracellular bridges—where desmosomes are present – EM—increase in number of desmosomes with increased cytoplasmic bundles (tonofibrils) • Membrane coating granules (MCG) appear in the cytoplasm of keratinocytes in upper layers of stratum spinosum – First appear near the golgi Apparatus EM of stratum spinosum LM of stratum spinosum Stratum Granulosum • Describe this layer in both the light microscope and electron microscope Stratum Granulosum • Describe this layer in both the light microscope and electron microscope – LM—large basophilic and irregularly shaped keratohyalin granules numerous – EM—KHGs are large, irregularly shaped not bounded by cell membrane, MCGs more numerous, migrate to periphery • So have both keratohyalin granules AND MCGs LM stratum granulosum Stratum lucidum • Describe its appearance in both EM and LM Stratum lucidum • Describe its appearance in both EM and LM – LM—nuclei not evident in flattened cells with pale if any staining – EM—organization of keratin filaments more regular Stratum corneum • Describe in EM and LM Stratum corneum • Describe in EM and LM – LM—cells flattened and scale like, cytoplasm uniform and acidophilic, no nuclei – EM—orderly aggregated Keratin filaments • Cell envelope—formed in cytoplasm adjacent to plasma membrane – Lipids from MCG cross-link to cell enveloperesists fluid penetration LM of Stratum lucidum and stratum corneum Melanocytes • Where do they originate from? • How do they deliver melanosomes? What is the process called? • What are melanosomes? Melanocytes • Where do they originate from? – Neural crest cells • How do they deliver melanosomes? What is the process called? – Via dendritic processes extending between keratinocytescytocrine transfer • What are melanosomes? – Vesicles in which melanin is formed More on melanosomes • They contain the enzyme tyrosinase which takes tyrosineDOPAdopaquinone • What happens in dark skin vs. light skin? More on melanosomes • They contain the enzyme tyrosinase which takes tyrosineDOPAdopaquinone • What happens in dark skin vs. light skin? – In dark skin melanosomes remain as single structures retained by keratinocytes – In light skin—melanosomes aggregate and are degraded by hydrolytic enzymes from lysosomes in stratum spinosum EM of melanosomes (labled 5) Langerhans Cells • Macrophage of the skin • Most frequent in the stratum spinosum Merkel cells •Found in stratum basale •Maybe mechanoreceptors •Many dense core granules may contain neurotransmitters Do you have thick skin? • What is different about thick skin vs. thin skin? Do you have thick skin? • What is different about thick skin vs. thin skin? – Thick skin lacks hair follicles and sebaceous glands – Two layers of skin are bound to each other by epidermal ridges—rete pegs and dermal papillae Dermis • Describe the papillary layer? • Describe the reticular layer? Dermis • Describe the papillary layer? – Just below epidermis and includes dermal papillae. Loose irregular ct and includes collagen, elastic fibers, GAGs, fibroblasts, etc • Describe the reticular layer? – Dense irregular ct (thicker than papillary layer) collagen, and other ct constituents Blood vessels of the dermis • Found in 2-3 plexuses • Subpapillary plexus—at the junction of the papillary and reticular layerscapillaries in papillary layer • Cutaneous plexus—at junction of reticular layer and hypodermis • Third plexus below hypodermis Nerve endings • What are the different types? Nerve endings • What are the different types and what are they for? – Pacinian corpuscles—deep pressure – Meissner’s corpuscles—light touch – Free nerve endings—pain, fine touch, heat and cold receptors – Ruffini corpuscles—in collagen fibers, respond when fibers are mechanically stressed/displaced Pacinian corpuscle – green arrow • For the gunners: whats the blue arrow? COWS • • • • Circle Of Wavy Shit • Peripheral nerve – this one is cut in cross section Meisner’s Corpuscles - green Accessory Organs • Hair– what is vellus hair vs. terminal hair • What are follicles? Accessory Organs • Hair– what is vellus hair vs. terminal hair – Vellus hairpeach fuzz – Terminal hairthicker hair, formed from vellus hair • What are follicles? – Invagination of epidermal cells into the dermis – Formation induced by protrusion of dermis, dermal papilla into the hair bulb More hair crap • What are the epidermal cells adjacent to the dermal papilla called? • What are they? More hair crap • What are the epidermal cells adjacent to the dermal papilla called? – Matrix cells • What are they? – Proliferative cells that correspond to the stratum basale – They give rise to different layers of the hair shaft—medulla, cortex and cuticle • What layers of the epidermis can be seen where on the hair? • What layers of the epidermis can be seen where? – Upper 1/3—all layers of the epidermis are evident – Middle 1/3—only lower two layers of epidermis – Lower 1/3—limited only to basal layer— continuous with the hair bulb I thought we needed a picture • Don’t worry, there will be plenty more later on What happens to matrix keratinocytes? • When they proliferate they form hard keratin • Matrix cells peripheral to the cells forming the hair shaft form the internal root sheath that surrounds the hair shaft within the follicle. Hair crap just goes on and on… • What are epidermal cells that form the hair follicle called? • And the dermis surrounding the hair follicle is called? • What about the basement membrane? Hair crap just goes on and on… • What are epidermal cells that form the hair follicle called? – External root sheath • And the dermis surrounding the hair follicle is called? – Connective tissue root sheath • What about the basement membrane? – Glassy membrane… its really thick – Between external root sheath and connective tissue sheath ALMOST FINISHED WITH HAIR • What is the arrector pili muscle? ALMOST FINISHED WITH HAIR • What is the arector pili muscle? – Bundle of smooth muscle attached to connective tissue of the follicle and the basement membrane of epidermis – Contraction in response to cold or fear makes the hair erect Phases of hair growth • And of course they couldn’t just call the phases of hair growth growing, receding, and resting because that would make sense. • Instead, its anagen, catagen, and telogen • At the end of anagen(growing) the catagen (receding) phase begins with follicle receding toward epidermal surface, dermal papilla lost • During telogen—hair shaft is released • Then the next anagen phase begins as new papilla formed and new hair shaft arises See papilla so it must be anagen Sebaceous glands • Simple, branched acinar glands • Derived from outpouching of basal cells in upper 1/3 of hair follicle • Glands secrete by HOLOCRINE mode of secretion • Lack myoepithelial cells • Become active during puberty • Acne is caused by obstruction of these glands Sebaceous glands galore Sweat glands • Eccrine (merocrine) sweat gland – Simple, coiled, tubular glands – Numerous, assoc. with skin all over the body – Two types of secretory cells? Sweat glands • Eccrine (merocrine) sweat gland – Simple, coiled, tubular glands – Numerous, assoc. with skin all over the body – Two types of secretory cells? • Light (clear) cells—more numerous than • Mucous (dark) cells—responsible for secretory product Sweat • What does sweat consist of? Sweat • What does sweat consist of? – Water and sodium chloride – Secretion from light cells released from apical surface of cells and into intercellular canaliculi – Between the base of the secretory cells and the basal lamina are myoepithelial cells—resemble smooth muscle – Ducts of glands extend to epidermal surface lined by stratified cuboidal epi. – Duct cells active in reabsorption of NaCl ions from secretory product – Reabsorption regulated by aldosterone Duct Secretory portion Apocrine sweat gland • Simple branched coiled tubular glands • Where are they located? • How are they different from eccrine glands? Apocrine sweat gland • Simple branched coiled tubular glands • Where are they located? – Axilla, pubic, areola, and circumanal regions – Note: I have a funny story to tell here, don’t let me forget • How are they different from eccrine glands? – Larger lumens, only one type of secretory cell present – Acidic secretory granules often visable DUCT SECRETORY PORTION Nail • Composed of nail plate with root and free edge • Nail consists of scales of cornified cells • What is the eponychium? • Hyponychium? Nail • Composed of nail plate with root and free edge • Nail consists of scales of cornified cells • What is the eponychium? – Region where nail emerges from epidermis at the junction with the stratum corneum • Hyponychium? – Where nail leaves nail bed to form free edge Nail the nail Image review Get ready…. Layers of skin – what you need to know • Epidermis (basale, spinosum, granulosum, lucidum, corneum) • Dermis (papillary layer, reticular layer) – Basically just CT • Hypodermis – Contains a lot of adipose Sweat glands • Apocrine and eccrine – Secretory portion – Duct – Myoepithelial cells – Eccrine have flat-topped epithelium and are found EVERYWHERE • SIMPLE coiled tubular – Apocrine have rounded/rough looking tops and are found in your pits and private areas • BRANCHED coiled tubular Hair follicles • Associated with smooth muscle of arrector pili muscles • Also associated with sebaceous glands that DO NOT have myoepithelial cells A little embryo action • Keratinocytes (corneum, lucidum, etc. etc.), hair follicles, sweat glands, sebaceous glands from ECTODERM – Epidermal stuff • Fibroblasts, smooth muscle cells, macrophages from MESODERM – Dermal stuff Thick skin – a ton of corneum; soles of feet and palms Close up • Pap. layer Retic. layer More thick skin The elusive lucidum corneum lucidum granulosum spinosum basale lucidum granulosum spinosum basale Epidermal pegs/rete pegs (white) – epidermis that bulges into dermis; anchor epidermis to dermis; dermal papillae (blue) is the dermis that bulges into epidermis. Got it? dermis • Papillary layer on top – Looser CT – Contains blood vessels, nerve endings (esp. in dermal papilla) • Reticular layer on the bottom – Denser CT (dense irregular CT) Thin skin – only a few corneum layers • Another clue = see hair and oil glands Now time for its close up of thin skin; notice the brown melanin pigment Hair follicle – must be thin skin Cross section hair follicle and oil gland Sebaceous glands – NOT in thick skin So much shit Oil gland Sweat gland Thin skin Reticular layer of dermis Adipose in hypodermis Blue = smooth muscle of arrector pili, note that’s its near a sebaceous gland Apocrine sweat glands – rough tops Remember the meissners corpuscle for touch in the dermal papillae??? Pacinian corpuscle in the dermishypodermis junction – onion rings DERMIS HYPODERMIS • Thick skin showing epithelial detail. Cornified (keratinized) stratified squamous epithelium makes up the epidermis. The stratum granulosum is very dark; the stratum lucidum is bright red. The stratum corneum is thick, and very pale. • Detail of epithelium of thick skin from the superficial to deep: • pale stratum corneum • bright red stratum lucidum • purple stratum granulosum • stratum spinosum THIS WAS ON OUR EXAM • Many desmosomes between cells (arrows). The cell membranes of the two cells are repeatedly interdigitated, giving the appearance of "intercellular bridges" in light microscopy. These bundles of keratin filaments are called TONOFIBRILS. • Detail of epithelium of thin skin, showing melanin in the basal layer. The pigment is produced by stellate shaped melanocytes of the dermal layer and then deposited in the basal cells of the epidermis. Melanocytes are of neural crest origin and have to be specifically stained in order to be seen. Thick skin – check out the corneum Papillary (finer strands) vs. reticular (thicker collagen strands) dermis • Meissners corpuscle in dermal papilla: This is a touch receptor Meissner’s The secretory portions of several sweat glands lie in clusters among the fat cells of the hypodermis, low in the picture. A Pacinian corpuscle is in the same area. These are the eccrine sweat glands of skin – they secrete their watery fluid by merocrine secretion. pacinian Eccrine sweat • Notice that the last slide was thick skin. It DOES have sweat glands, just no hair follicles or oil glands. Think about it. Does anyone you know have hairy feet? I hope not. Also, makes sense why the lotion business is huge – no oil glands on hands! Eccrine sweat glands and ducts • Detail of sweat gland. The darker circles in the lower part of the field are ducts; the lighter cross-cuts above are the secretory portions. Eccrine sweat gland The ducts are distinguished by their stratified cuboidal appearance and the fact that they are much denser eccrine eccrine Apocrine – ruffled tops… where are these found??? ;) apocrine Apocrine! Apocrine sebaceous (1) hair shaft; (2) connective tissue sheath; (3) external root sheath; (4) internal root sheath; (5) dermal papilla; (6) germinal matrix • Hair follicles of scalp, with associated pale sebaceous glands. The follicles extend down into the hypodermis, which is largely adipose tissue. Notice the arrector pili (orange) muscle running diagonally toward the upper right-hand corner of the field. At the base of a hair follicle sebaceous glands (red) are found. These glands secrete oil into the follicle. They secrete via a process called "holocrine secretion" in which the cell fills with secretory material and then essentially distintegrates; the whole cell is shed • Detail of sebaceous gland. Cells look foamy because of loss of lipid droplets during tissue fixation. This gland exhibits holocrine secretion, in which whole cells swell up, degenerate, and are desquamated. The secretion is emptied into the hair follicles and eventually reaches the surface of the skin. Identify the layer identified by the arrow •Hints: •You are in the epidermis •Answer: Stratum spinosum •You know because you could see the intracellular bridges Identify •Hints: This is cut in cross section! •Answer: It’s a hair follicle Identify • Hints: • Answer: – It’s a pacinian corpuscle – You know because of its onion-like appearance Identify •Hints: –What can you see on the slide? –What type of tissue is it? •Answer: Arrector Pili muscle Identify •Hints •What type of tissue? •Is it associated with a hair follicle? •Answer: –Eccrine gland What is indicated by each arrow? •Hints –What is the main structure in the image? •Answer: –Blue arrow—vascular pole –Green arrow—urinary pole Identify •Hints: •C-shaped cartilage •Answer: –trachea Identify •Hints –epithelium –Presence of glands •Answer: –False vocal fold/cord Identify Hints • What type of tissue? • Is it associated with hair? • Answer: – Sebaceous gland • What mode of secretion? – Holocrine Identify blue arrow •Hints: –Where are you? •Answer: –Rete pegs/epidermal ridges Identify •Hints: •Layer of epidermis •Answer: –Stratum basale 1? 2? • 1. (1) arrector pili muscle; (2) sebaceous gland What is at the white arrow and what layer(s) of the skin are shown in this image? • sweat gland (secretory unit and duct) in the hypodermis • What type of skin is this? THIN!!!!!!! – you can see a snip of arrector pili at the bottom as a clue! Identify the multicellular structure at the tip of each of the numbered arrows. (1) Meissner's corpuscle; (2) dermal papilla What is the brown material at the tips of the arrows? MELANIN WHEW!!!!