BRS Mock 4 derm1, pituitary, airways Flashcards
How does skin development start?
Single layer of cuboidal cells form and make up the surface ectoderm. Secondary layer of squamous non keratinising cells form on top and these cells are know as the periderm.
What do the periderm cells do in early skin development?
Secrete vernix caseosa which is a white waxy protective substance.
What happens later on at week 11 of skin development?
Basal layer of cuboidal cells proliferate to form multilayer intermediate zone. Basal layer of cuboidal cells is now know as the stratum basale.
What happens at week 20 of skin development?
Further differentiation forms spinosum, granulosum, lucidium and corneum.
Where do hair follicles develop from?
Stratum basale.
What are the epidermal ridges that protrude into the dermis known as?
Rete ridges.
What is the superficial layer of the dermis known as?
Papillary dermis.
What are the skin layers from top to bottom?
Epidermis, basement membrane, dermis and subcutaenous fat.
What cells make up the epidermis?
Keratinocytes.
Where does cell division occur in the skin?
Stratum basale.
What are the layers of the epidermis from bottom to top?
Stratum basale, stratum spinosum, stratum granulosum, Stratum lucidum and stratum corneum.
What occur as you go up the layers of the epidermis? And why is this a problem in some diseases?
Differentiation and flattening of cells. This process can be accelerated in skin diseases such as psoriasis.
Why is the stratum lucidum different from other epidermal layers?
Only present in palms and soles.
Describe the stratum lucidum?
Only present in palms and soles. No nuclei or organelles.
What does the keratinocyte cytoskeleton contain?
Actin containing microfilaments. Tublin containing microtubules. Intermediate filaments which are the keratins.
What is the function of desmosomes?
Major adhesion complex. Anchor intermediate filaments to cell membrane and bridge adjacent keratinocytes. Provide strength.
What are gap junctions and what do they do?
Contain intercellular channels. Form connections between cytoplasm of adjacent keratinocytes.
What complex/junction inbetween keratinocytes are essential for cell synchronization and metabolic coordination?
Gap junctions.
What are adherens junctions and what do they do?
Transmembrane structures that engage with the actin skeleton.
What do tight junctions do?
Role in barrier integrity and polarity.
What epidermal cells other than keratinocytes are present?
Melanocytes, langerhans cells, merkel cells and mast cells.
What are merkel cells?
Mechanosensory receptors.
- involved in sensation.
What does the basement membrane contain?
Collagens, laminin and integrins.
What are the most prominent types of collagen in the basement membrane?
IV, VII
Function of rete ridges?
Strength and provides specialised environment for epidermal stem cells.
What are the two main layers that make up the dermis?
Papillary dermis and reticular dermis.
Describe the papillary dermis
Superficial layer of the dermis that is made up of connective tissue and is highly vascular.
Describe the reticular dermis
Dense connective tissue that forms bulk of dermis.
What proteins does the dermis contain?
Collagen, fibrillin and elastin.
What glycoproteins does the dermis contain?
Fibronectin, fibulin and integrins.
Where is the ground substance located in the dermis?
Between dermal collagen and elastic tissue.
What is the primary cell in the dermis?
Fibroblasts.
What stimulates eccrine sweat glands?
Cholinergic nerves and adrenergic nerves.
What stimulates apocrine sweat glands?
Adrenergic nerves.
What is the function of the arrector pili muscle?
Arrector pili muscle is connected to the hair follicle. Contraction of the muscle causes hair erection and goosebump.
Where are encapsulated receptors found?
In the dermis.
Where are non encapsulated receptors found?
Epidermis.
Describe the meissner’s corpuscle?
Encapsulated, unmyelinated mechanoreceptor present in the superficial dermis. Most concentrated in thick hairless skin.
What is the meissner’s corpuscle responsible for?
Light touch and slow vibration.
Describe the ruffini corpuscle
Encapsulated mechanoreceptor. High density around fingernails.
What is the ruffini corpuscle responsible for?
Sensitive to skin stretch to monitor slippage of objects.
Describe the pacinian corpuscle
Encapsulated rapidly adapting mechanoreceptor.
What is the pacinian corpuscle responsible for?
Surface texture - deep pressure and vibration.
Describe the merkell cell
Non encapsulated mechanoreceptor that is a modified epidermal cell.
What is the merkell cell responsible for
Light sustained pressure.
How do langerhans cells detect pathogens?
Use TLRs to detect PAMPS. This results in activation of innate immune system and induction of adaptive response.
What do langerhans cells do in absence of danger?
Promote expansion and activation of Tregs.
What do langerhans cells migrate through?
Tight junctions.
What immune cells are present in the skin?
Tissue resident T cells, macrophages and dendritic cells .
How are keratinocytes involved in immunity?
Produce antimicrobial peptides.
How do peptides hormones create a signal?
Transduce signal using 2nd messenger systems.
How are steroids released compared to peptides?
Released immediately while peptide secretion is regulated.
How are peptides hormones stored?
Stored as vesicles.
What is Rathke’s pouch?
Is an ectodermal invagination of the roof of the developing embryonic mouth.
What does growth hormone do?
Body tissues growth and release of IGF-1 from liver.
What can a pituitary tumour result in?
Compression of optic chiasm can lead to bitemporal hemianopia. Prevents transmission of information from lateral visual fields to occipital lobes.
Symptoms of agromegaly?
Increased hand and feet size. Macroglossia. Prominent nose.
Explain the release of thyroxine
Axon terminals of parvocellular neurones release thyrotrophin releasing hormone (TRH) into hypophyseal portal system. TRH travels through the capillaries of the portal system to anterior pituitary gland. TRH binds to thyrotrophs and stimulates release of TSH. TSH leaves pituitary gland via the blood and travels to thyroid gland to stimulate release of thyroid hormone.
Explain release of arginine vasopressin and oxytocin
Arginine vasopressin produced in supraoptic nucleus. Oxytocin produced in paraventricular nucleus. Hormones travel down neuronal axons in pituitary stalk. Enter posterior pituitary and stored. Excitation of hypothalamic magnocellular neurones releases AVP or oxytocin. These diffuse into capillaries.
Physiological action of arginine vasopressin?
Anti-diuretic hormone, vasoconstrictor and stimulates ACTH release from anterior pituitary.
Arginine vasopressin anti diuretic mechanism?
AVP binds to V2 receptor. Leads to aquaporin-2 channels bind to apical membrane of kidney duct cell. Allows water to move into duct cell from urine and so this leads to more concentrated urine.
Physiological action of oxytocin?
Causes contraction of myometrial and myoepithelial cells leading to delivery of baby and milk ejection.
Explain process of lactation?
Mechanical stimulation of nipple. Action potentials in ascending sensory pathway, inhibit dopamine release from dopaminergic neurones and stimulate oxytocin releasing neuron activity. Inhibition of dopamine leads to less inhibition of anterior pituitary lactotrophs. Oxytocin produced in hypothalamus and released from posterior pituitary. Increased plasma prolactin leads to increased milk production in mammary glands. Increased plasma oxytocin leads to increased milk ejection.
What nuclei is AVP produced in?
Supraoptic nucleus.
What nuclei is oxytocin produced in?
Paraventricular nucleus.
Describe the structure and function of type 1 alveolar cells.
Squamous and very thin and facilitate gas exchange.
Describe the structure and function of type 2 alveolar cells.
Granular and cuboidal. Replicate to replace type 1 alveolar cells. Secrete pulmonary surfactant. Secrete antiproteases.
What does pulmonary surfacant do?
Reduces surface tension prevents alveolar from collapsing.
What other cells can you find in the alveolar region?
Macrophages and stromal cells.
How is the nose adapted for breathing?
Conchae in the nose are highly vascular. This warms and humidifies nasally inhaled air. Nasal hairs filter out large particles.
What produces mucus in the airways?
Goblet cells and submucosal glands.
Two kinds of cells in the submucosal gland? What are their functions?
Mucous and serous cells. Mucuous cells secrete mucus. Serous cells secrete anti bacterial enzymes.
Describe ciliary structure?
Axoneme that has a 9 + 2 microtubule arrangement.
What is the movement of mucus by cilia called? What is the function?
Mucociliary clearance. Physical barrier to infectious agents.
What does inflammation of airway smooth muscle cell result in?
Hypertrophy and proliferation of smooth muscle. Cytokine and chemokine secretion. Nitric oxide and prostaglandin release.
What nerves controls airway function?
Parasympathetic and sensory nerves.
Explain airway constriction by nerves
Solid enters airway and detected by sensory receptors. Excitation of sensory nerves up to brain stem, Excitation of parasympathetic nerves cause release of ACh from preganglionic terminal ends. This results in release of ACh from post ganglionic fibres. ACh cause contraction of smooth muscle in airways and mucus secretion.
