15.1 - Cancer Biology Flashcards
Integument
- Composed of 2, often 3 layers
1) Epidemis = - epithelial layer
2) Dermis = - CT layers with 2 divisions:
- A) papillary layer
- B) reticular layer
3) Hypodermis = - deep to the dermis
- rich in adipose tissue
- not always present
Dermal Papillae
- bumps/papillae extending from dermis into epidermis
- FXN: increased mechanical strength
- epidermis in between them forms interpapillary (rete) pegs
Interpapillary (rete) pegs
= epidermal tissue lying in between the dermal papillae
Keratinocyte
= principle cell of dermis
- its stem cell is located in the stratum basale = most basal layer
- daughter cells form the stratum spinosum
- in the stratum spinosum –> neighboring keratinocytes connect to each other via desmosomal junctions
Stratum granulosum
= visible in thick skin only (thin skin lacks this visible layer in LM)
- cells here contain visible keratohyaline granules
Stratum Lucidum
= consists of dying cells that still retain cytoplasm
- visible in thick skin only (thin skin lacks this visible layer in LM)
Stratum corneum
= top layer of skin
- conceits of keratin sheets bound by lipids and keratohyaline
- the lipids function to form a water barrier
- keratohyaline = a fillagrin precursor that acts as a glue for the keratin
- In EM –> lipids with associated enzymes are visibly contained within distinctive lamellar bodies
Keratohyaline
= fillagrin precursor
- acts as a glue for keratin
- present in the keratin sheets of the stratum corneum
- present in the granules of the cells of the epidermal stratum granulosum layer
3 minority cells in the epidermis
1) Melanocytes
2) Langerhans’ cells
3) Merkel Cells
- both 1 and 2 are migratory
Melanocytes
= minority cell type in epidermis
- export melanin pigment to surrounding keratinocytes –> via cytocrine transfer of melanosome vesicles
- derived from neural crest cells
Langerhans cells
= minority cell type in epidermis
- resident APC (dendritic cells)
- derived from hematopoietic CLP cell
- cells of the immune system
- labels with CD1a in video
Merkel Cell
- mysterious cell (little known)
- interfaces with the nervous system
- participates in mechanosensation
Meissner’s corpuscles
= sense light touch
- reside in papillary dermis
Pacinian Corpuscles
= sense pressure
- reside deep in the dermis or hypodermis
Free nerve endings
- sense pain and temperature
- also present in dermis
Apocrine sweat glands
= large tubular serous galnds
- found only in axilla and armpits
- majority of their secretions (in humans) are eccrine in nature
(anal scent glands of dogs are apocrine sweat glands that secrete apocrine product)
Hair follicle
= specialized invagination of the epidermal layer
- hair shaft = center of hair follicle - surrounded b root sheath
- dermal papilla of the hair = region at the base of the follicle from which hair grows
- are often found in associated with sebaceous glands + arrector pili muscle that functions to erect the hair –> meet follicle in bulge region
- stem cells for the follicle are found in this bulge region
Hair shaft
= center of hair follicle
- often missing from histological sections
- surrounded by root sheath
Root sheath
= surrounds the hair shaft at the center of the hair follicle
Dermal papilla of the hair
= region at the base of the hair follicle
- location where hair grows from
Three distinct phases of hair growth
1) Anagen
2) Catagen
3) Telogen
Sebaceous glands
- often found in association with hair follicles at the bulge region
- can exist without accompanying hairs (ex. on the nipple)
Arrector pili muscle
- associated with hair follicles
- FXN: to erect the hair
Bulge region
= location of the stem cells for the hair follicle
- location where arrestor pili muscle and sebaceous glands contact the hair follicle
Mammary Gland
- evolutionarily derived from sweat glands
- modified during evolution to produce colostrum and subsequently milk for the postnatal nourishment of young
- stroma = CT and adipose tissue
- parenchyma = organized into lobes + lobules
Colostrum
- evolutionary product of the sweat glands - precursor to the milk product of the mammary glands which are derived evolutionarily from sweat glands
Stromal breast tissue
- includes connective and adipose tissue
Parenchymal breast tissue organization
into lobes and lobules
4 types of mammary glandular cell secretions and the respective products
1) Apocrine secretion - lipids
2) Merocrine secretion - proteins and carbohydrates
3) Transcytosis - antibodies
4) Active transport - vitamins, salts, hormones
Ductal system for the transfer of milk
Lacteriferous duct System
1) small intralobular ducts
- within the lobules
2) medium interlobular ducts
- between the lobules
3) larger lactiferous ducts
- (no specific name)
- lead from lobes to the nipple
- these ducts anastamose near the nipple in lactiferous sinuses
Growth of lactiferous duct network
- by branching morphogenesis in stages throughout the lifetime
A) at birth
= limited network
B) at puberty - estrogen principally influences the expansion of the network
- progesterone produced during puberty stimulates the development of glandular cells
C) during breast feeding and perinatally - PRL stimulates the glandular activity
- Oxytocin mediates neurally-controlled “let-down” reflex
What is the epidermis
= epithelial layer of the integument - contains 3-5 sublayers depending on whether skin is thick or thin - thick skin has 2 added layers A) stratum lucidum B) stratum granulosum
What are the 5 layers of the epidermis - outside inwards (Note: would only be three in thin skin, indicate the two that are present in thick skin only)
1) Stratum corneum
2) Stratum Lucidum
- thick skin only
3) Stratum granulosum
- thick skin only
4) Stratum spinosum
5) Stratum basale
Describe the Stratum Corneum
= cornified outermost laer
- consists of mostly accumulated intercellular cross-linked keratin proteins
Describe the Stratum Lucidum
- in thick skin only
- relatively translucent layer
- cells have lost their nuclei
- cell are loosing much of cytoplasm/volume and desmosomal connections
Describe the stratum granulosum
- in thick skin only
- contains special type of granules = keratohyaline granules + lamellar granules (membrane-coating granules)
Describe the stratum spinosum
- layer of relatively healthy keratinocytes
- makes up the majority of skin thickness
Stratum basale
- most basal layer of the epidermis
- contains a small population of stem cells
- sits against BM
What is the dermis
- CT layer of the integument
- contains 2 divisions
1) Papillary dermis
2) Reticular Dermis
What are the two divisions of the dermis
1) Papillary dermis
2) Reticular Dermis
Describe the papillary dermis layer
- immediately adjacent to the BM of epidermis
- loose irregular CT layer
- surrounds dermal papillae = evaginations of CT layer into the epidermis
What are dermal papillae
= evaginations of the papillary dermis CT (loose irregular) into the epidermis
- tips contain meissner’s corpuscles (sensory FXN)
- tips contain extensive capillary network
- corresponding epidermal structures = interpapillary pegs
What are interpapillary pegs
= the corresponding epidermal structures to the dermal papillae
Describe the reticular dermis layer
- deeper dermal layer
- dense irregular CT
- often contains significant quantities of elastic fibers
Describe the hypodermis
= extra layer of adipose tissue below the dermis
What are the 2 granules types found in the stratum granulosum layer of cells and the function of each type
1) kerato-hyaline granules = very dark in EM and dark in the LM
- FXN: produce cross-lnked keratin in these cells + form a sheet-like substance that will form the tough upper layers of skin
2) lamellar granules = membrane coating granules
- FXN: produce lipid secretion - becomes extracellularized + serves to insulate the epithelium against water loss through the skin
What are melanosomes
= the special intracellular compartments/vesicles in melanocytes where they produce the melanin pigment
Describe melanocytes
- spinous cells that extend processes among neighboring keratinocytes
- unlike the keratinocytes - they do not have desmosomal connections and are therefore somewhat free to migrate within the epithelium
- in H and E - are notable for lack of desmosomal connections –> so usually see shrinkage around neighboring keratinocytes and no pigment in them
What are the 3 steps in synthesis of pigment and the degradation of it
1) Premelanosome formation
- specialized intracellular organelle (vesicle) is formed = future melanosome
2) Synthesis of melanin in early melanosome
3) Melanosome secretion
- transported to distal arms of spinous processes of the melanocytes
- are secreted via cytocrine secretion (cell to cell trans secretion
- melanosomes end up in neighboring keratinocytes (generally those in stratum basale)
4) Melanosome degradation in keratinocytes
Describe a hair follicle
- rarely will find an entire hair follicle present in 1 section because it is a long structure
= invagination of integument surface - integument has a BM continuous around the follicle forms a structure = glassy membrane
- cells of epidermis continue into hair follicle as root-sheeth
What is the glassy membrane
- structure formed from the BM continuing from the integument around the hair follicle
- thick structure - visible in LM
Describe the root sheath and the 2 divisions of it
= cells of epidermis continuing into hair follicle
- divided into 2 parts
1) External Root sheath (ERS) = relatively apical and external
2) Internal root sheath (IRS) = relatviely basal and internal
- consists of sublayers
A) Henle’s layer of IRS
B) Huxley’s layer of IRS
What is the hair bulb
= structure that hair is grown from
- exists in base of hair follicle
- most often found in hypodermis layer
- or if hypodermis layer is absent then it will be found very deep in dermis layer of skin
Describe the shaft of hair and the 3 portions comprising it
- sometimes it is not present in LM
- morphology of it is difficult to preserve and therefor is rare to see 3 layers of hair?
- 3 portions of the shaft
1) Inner portion = medulla
2) Middle portion = cortex
3) outer portion = cuticle
Describe the bulge region
= cellular structure of desquamated cells present in hair bulb
- important region because it contains the stem cells for the hair follicle
- 2 structures that are visible in LM attach to the hair follicle in this region
1) Sebaceous gland - holocrine secreting gland (cells undergo apoptosis in apex of gland and contribute entire contents to secretion that ends up between the hair shaft and ERS)
- stratified cell layer
- produces sebum (waxy substance)
2) Arractor pili muscle - function to make hair stand straight
Describe the mammary glands
= modified sweat glands
- FXN: produce milk and other substances for the nourishment of newborn in females
- present in rudimentary form in prepubescent individuals and males
Describe the stromal structure of the mammary glands
- bulk of which is dense irregular CT or adipose tissue
Describe the parenchyma structure of the mammary gland
- lactifierous ducts (drain to the nipple from lactiferous sinus)
- each duct drains 1 lobe of the breast
Discuss the general morphology/organization of breast in LM
- structure of a lobe is rarely apparent in LM because the lobes are usually bigger than average tissue block
- each lobe is divided into multiple lobules
- a lobule can be identified by
A) loose irregular CT
B) hypercellularity of the (loose irregular) CT - many of which are lymphocytes and/or plasma cells in active breast will contribute antibodies via transcytosis into product of breast - outside lobule = the normal stroma of the breast - made up of dense irregular CT + adipose tissue
Describe the lobular morphology in an inactive breast
- lobules consist entirely of ducts
- a lot of CT
Describe the lobular morphology of an inactive breast
- stem cells in tips will elaborate and form complicated acinar structures = secretory glands
- lobules empty in a particular order so compare lobules with adjacent lobules - some may be filled and others may be relatively empty
- lobules - consists entire of ducts, much less CT, have elaboration of secretory alveoli filling them
- abundance of lymphocytes
Describe the morphology of the lactiferous ducts
- notable for absence of secretions
- will be single cuboidal cell layer
What are the 2 specific categorizations of the lactiferous ducts and their morphologies
1) Intralobular lactiferous ducts
- within a lobule
- surrounded by loose CT
2) Interlobular lactiferous ducts
- harder to find
- between a lobule
- surrounded by dense CT
Describe the morphology of secretory cells of mammary glands
- contain lipid inclusions (sitting apically in the cell; secreted via apocrine secretion to the lumen)
- also contain significant protein components to the milk - secreted by merocrine secretion apically into the lumen
Describe myoepithelial cells including their role and location in the mammary gland
- surround glandular and ductal portions of the tissue
- help to expel product
- can occasionally be seen in the LM
