Session 5 Flashcards
What is the definition of a gland and secretion?
epithelial cell
aggregate of epithelial cells
specialised
secretion of a substance
production
release
material
cell or aggregate of cells
How are glands classified?
structure
release of products method
Describe the endocrine glands
secrete directly into blood flowing through them secrete hormones ductless e.g. pituitary gland anterior and posterior thyroid gland parathyroid gland
all epithelium;ial cells secrete hormones in the gland
Describe exocrine glands
ducted secrete into location or region of the body secrete enzymes or lubricants e.g. salivary gland pancreas mammary sweat glands sebaceous glands lachrymal glands
only cells at the apex of the duct secrete the products
Describe the steps involved in the generation of glands (in utero)
- growth signal received
- proliferation + extracellular degeneration enzymes
- epithelial cells invade
- exocrine gland; canalicularisation
- endocrine glands; angiogenic factors stimulate blood vessel growth
- link to mother cells broken
How does branching occur? (lung example)
basic FGF10 immature fibroblasts epithelial cells move to signal two fates: - tubule elongation - tubule branching
What are the different shapes of gland ducts?
exocrine
cells lining ducts
cells make secretory products
simple tubular, simple branched tubular
compound tubular
simple alveolar, simple branched alveolar
compound alveolar, compound tubuloalveolar
What are myoepithelial cells?
cells at secretory ends change morphology and class
these are cells
have features of epithelial and smooth muscle cell
help eject secretions from duct
Explain the breast example
same process development as salivary glands
developments stops until puberty
oestrogen and progesterone restarts breast production
prolactin stimulates production of breast milk secretions
6th week therefore men too
What three ways can you classify glands?
merocrine - fusion vesicles apical membrane apocrine - partial loss cytoplasm holocrine - complete loss cytoplasm cytocrine - cells released as secretion
What are the two pathways for merocrine secretion?
exocytosis
regulated secretion
needs Ca
secretory granules accumulate large vesicles released by exocytosis
constitutive secretion
secretory product not converted to granules packaged into small vesicles
continuously released to cells surface
repopulate plasma membrane with plasma proteins
Describe the process for regulated secretion in more detail
active process contents of vesicle anything within cell active secretion needs specific signal vesicle migrates to cell surface with Ca ions membrane of vesicle fuses cargo released
Describe the apocrine secretion example of the breast
neonatal period fats secreted milk proteins free ribosomes Golgi apparatus (merocrine)
during lactation
fats and proteins
apocrine
Describe the holocrine secretion example of the sebaceous gland
secretory cell fills up organelles degenerate cells die plasma membrane breaks dead cells replaced
if attached to hair
same process
Describe how the Golgi apparatus is involved in secretion
might need to research
What is glycosylation of proteins/lipids? Describe the functions of it
covalent attachment
sugars
enzymes
forms glycoproteins and glycolipids
roles aid folding prevent protein digestion prevent lipid digestion cell recognition cell to extracellular matrix attachment
critical function
50%
What is exocytosis and endocytosis?
exo
secretion of molecules
outside cell
vesicle fusing to membrane
endo
engulfing molecules
inside cell
vesicle formation
What is phagocytosis and pinocytosis?
phago
cells envelop/ engulf
cells/ particles
cells of immune system
pino
liquid droplets ingested by cell
all cells
Describe the four types of processes of transcytosis
1. molecules move aqueous channels 2. lipid cell membranes 3. molecules appropriate characteristics transported by carrier proteins counter transport process 4. impermeable bind to cell surface receptors endocytosis exocytosis
eg
- amino acids
- steroid hormones
- thyroxine transport
- cholesterol
What are the types of glandular control?
humoral stimulus feedback loops neural stimulus salivary glands hormonal stimulus endocrine glands
Describe the feedback loops for each stimulus
use picture on slide
What is neurocrine communication?
eg hypothalamus to pituitary
hypothalamo- hypophyseal portal system
learn diagram (need to know above system)
What does the hypothalamus deal with and produce?
thermoregulation
plasma osmolality
lactation
etc
vasopressin and oxytocin
six hormones travel via hypothalamo- hypophyseal portal system to anterior pituitary
What are portal systems?
portal vs circulatory
Why is there always a small concentration of pituitary hormones in the blood?
all of the pituitary hormones are subject to constitutive and regulated secretion
What happens from week 5 onwards in embryology in the development of the endocrine system?
on ventral surface
pituitary- from neurohypophyseal bud and hypophyseal pouch
thyroid- from floor of pharynx
parathyroid- develop from third and fourth pharyngeal pouches
adrenals- from intermediate mesoderm and neural crest
pancreas- from the foregut
Describe the thyroid gland
anterior trachea of neck
left lobe and right lobe, connected by a narrow isthmus
a normal thyroid can’t be easily palpated on a physical examination
under the actions of TSH and TSAb’s produces T4 and T3
What are the clinical consequences of autoantibodies in the thyroid gland?
high t3 and t4 = hyperthyroidism
Graves disease
presents with anti TSH and TSI antibodies
low t3 and t4 = hypothyroidism
Hashimotos disease
presents with anti- TPO and anti- TG antibodies
Describe the parafollicular cells
neuroendocrine cells migrate to thyroid during thyroid development
produce calcitonin
independent of thyroid hormone synthesis
role to monitor plasma Ca concentration levels and decrease if too high
major effect: inhibits osteoclast activity in bone
minor effect: inhibits Ca and phosphate reabsorption in tubules
Describe the parathyroid gland
constantly monitors plasma calcium concentrations
when conc of Ca is low, the gland makes parathyroid hormone
PTH releases calcium from bones and absorbs more Ca from the GI tract
negative feedback loop
Why is calcium important?
most important for nervous, skeletal and muscular system
allows muscles to contract
this is why parathyroid disease causes symptoms of the brain, muscles and bones
Describe the structure of the adrenal gland
right gland left gland medulla cortex right and left have their own blood supply
Describe the adrenal medulla and the adrenal cortex
medulla composed of a parenchyma of large epitheliod cells (not epithelial as have no basement membrane)- chromaffin cells
myelinated, presynaptic sympathetic nerve fibres pass directly to chromaffin cells
when nerve impulses reach the chromaffin cells they release adrenaline and noradrenaline
chromaffin cells equivalent of post synaptic neurones
cortex has three layers; zona glomerulosa, zona fasciculata and zona reticularis
What is the stress response?
activation of the response initiates a number of behaviour and physiological changes that improve an individuals change of survival when faced with homeostatic challenges
behavioural:
Where are the principal effectors of the stress response located?
s
What are the short term and long term responses to stress caused by the adrenal gland?
sq
Describe the structure of the pancreas
a
What are the cells that make up the endocrine gland component?
s
Name the exocrine and endocrine functions of the pancreas
s
