receptor/ligand interaction, not endocrine/secretion
rounded, few junctional complexes, do not surround lumen (epithelioid)
spherical, surround central lumen, single layer with polarity and junctional complexes
Four types of secretory product
proteins - anterior pituitary (high RER and Golgi), amines - adrenal medulla (similar, but less RER), steroids - ovary (high SER and lipid droplets), and eicosanoids - mast cells (similar to steroid)
Bilobed with connecting isthmus, ventral to trachea/inferior to thyroid cartilage, produces T3 (tri-iodothyronine) and T4 (thyroxine) which elevate the basal metabolic rate, has follicles and C cells
Thyroid follicles - protein colloid, simple epithelium, thin connective tissue connects to capillary, can be squamous to columnar, height corresponds to activity level. Have much RER, Golgi, lysosomes, and mitos, but few secretory droplets.
In response to TSH, thryoglobulin (125 Tyrosine residues) made in RER, then glycosylated in Golgi, then exocytosed. Iodide pump brings in iodide from basal, then transcytosed and oxidized to iodine. Immediately, thyroglobulin is iodinated to completion and stored as iodothyroglubulin
TSH stimulates, thyroid cells endocytose iodothyroglobulin and form phagosomes. Then form secondary lysosomes. Then cleaved to T3/T4. T3 is converted to T4 in target cell.
Thyroid hormone deficiency during fetal development (thyroid hormone and growth hormone are synergistic). Defects in CNS development and stunted growth
Hypothyroidism = mental/physical sluggishness, cold intolerance, loss of appetite, weight gain.
sleeplessness, heat intolerance, increased appetite, weight loss
autoimmune disorder, Abs made to TSH receptor and mimic TSH action. increased hormone production, mimics hyperthyroidism
enlarged thyroid, lack of iodine in diet or defects in T3/T4 production. Gland is not neoplasmic or overactive
Produces in Thyroidal C cells (never tough follicle lumen, sit next to capillary) in response to high blood calcium. Stimulates osteoblasts and inhibits osteoclasts to increase bone formation
two pairs on dorsal surface of thyroid gland. Made of chief cells and oxiphyl cells (no known function, lots of mitos, increase in number with age, larger than chief cells)
Main cells in parathyroid, secrete parathormone in response to low blood calcium concetration.
In bone - inhibits osteoblasts and stimulates osteoclasts. In kidney - stimulates phsosphate excretion and inhibits calcium excretion. In intestine - stimulates calcium absorption while using active metabolites of vitamin D.
low blood calcium, increased excitability of the nervous system, convulsions, and muscle tetany
high blood calcium, fragile bones, calcium deposits in kidney tubules and blood vessels
suprarenal glands, superior poles of the kidney. Cortex (develops from mesoderm) and Medulla (develops from neural crest, similar to sympathetic ganglia)
Adrenal Medulla blood supply
two sources, 1) medullary arteries pass through cortex to medullary sinusoids (arterial) 2) cortical arteries -> capillaries in cortex (sinusoids) -> receive adrenal cortex hormones -> medullary sinusoids (venous) -> drained by veins
from inside to outside = zona reticularis, xona fasiculata, and zona glomerulosa
Outermost adrenal cortex, arched cords (high SER, golgi, and mito). secrete mineralcorticoids = aldosterone. under renal control
In response to low blood pressure, kidney secretes renin, which converts circulating angiotensinogen to angiotensin I, which is then converted to Angiotensin II.
targets kidney, salivary, and sweat glands. release stimulated by angiotensin II (from kidney). stimulates kidney distal convoluted tubule to absorb sodium. sodium/water is retained, and potassium is excreted (Na/K ATPase)
central adrenal cortex, large, polyhedral, pale staining cells in two cell wide columns with a sinusoidal capillary. secrete glucocorticoids = cortisol, under control of pituitary gland (ACTH).
glucocorticoid released from zona fasciculata (Adrenal cortex) in response to stress. Stimulated by ACTH from pituitary gland. regulats carb/protein metabolism. stimulated anabolic activity in liver, and catabolic activity in adipose/muscle. fats, sugars, and AAs used to glycogenolysis, gluconeogenesis, and enzyme synth. (PNMT methylates norepinephrine to epinephrine) overexposure depressed immune system.
inner adrenal cortex, cells in anastomosing cords (web) separated by fenestrated capillaries. source of weak androgens. regulated by ACTH from pituitary.
large, palely staining epitheliod cells (chromaffin cells = sympathetic neurons with rudimentary dendrites and no axons). secretes epinephrine/norepinephrine, controlled by preganglionic sympathetic neurons.
increases heart rate/cardiac output without increasing blood pressure, also increases basal metabolic rate. producing cells lie in regions fed by cortex blood.
zona glomerulosa (outer adrenal cortex) overproduces aldosterone. high blood pressure/increased potassium excretion
zona fasciculata (central adrenal cortex) overproduce cortisol. can be adrenal tumor, but most often excessive ACTH from pituitary (adenoma), rapid weight gain (trunk and face, central obesity) and excessive sweating
increases blood pressure by vasoconstricting peripheral ateries, without affecting heart rate/cardiac output (made from larger, denser granulate in cells)
Pars Distalis, Pars Intermedia, and Pars Tuberalis
Subdivisions of Neurohypophysis
Pars Nervosa, Infundibulum (Median eminence & Infundibulum stem)
outgrowth of oral cavity, glandular epithelium, pars distills is major lobe, epitheloid cords, fenestrated capillaries, and reticular connective tissue
outgrowth of brain (neural secretory tissue), pars nervosa is major lobe, unmyelinated axons of hypothalamic neurons, pituicytes (glial cells), blood vessels, and stored neurosecretory material (herring bodies)
Pituitary Portal System
superior hypophesial ateries -> primary capillary plexus in the infundibulum -> pituitary portal veins -> secondary capillary plexus in the adenohypophysis -> hypophyseal veins -> pars distalis
Pars tuberalis blood supply
superior hypophyseal arteries and primary capillary plexus
Pars nervosa blood supply
direct blood supply from inferior hypophyseal arteries -> capillary plexus then drain into dural venous sinus
blood supply entering and leaving capillary as same category
Cell types of Adenohypophysis
Chromophobes, Chromophils, which are Acidophils - eosin/pink (somatotrophs and mammotrophs) and Basophils - hematoxilin/blue (gonadotrophs, thyrotrophs, and corticotrophs)
the axonal connection between the paraventricular and supraoptic nuclei of the hypothalamus and the pars nervosa to the hypophysis
Hormones secreted by the adenohypophysis
ACTH, GH (STH), FSH, LH, PRL
Hormones secreted by the neurohypophysis
oxytocin, vasopressin (ADH)
adrenocorticotropic hormone. stimulates the zona fasciculata (the central adrenal cortex) to produce glucocorticoids (cortisol). Stimulated by CRH (corticotroph releasing hormone) from hypothalamus
growth hormone, somatotropin (STH). stimulated liver to produce somatomedin (stimulates bone growth and metabolism in most cells), Stimulated by SRH (somatotroph releasing hormone) from hypothalamus
thyroid stimulating hormone. stimulates thyroid to produce T3/T4, which increase basal metabolic rate. Stimulated by TRH (thyrotroph releasing hormone) by hypothalamus
follicle stimulating hormone. In females, stimulates ovary to produce estrogen (for oocyte/uterine growth). In males, stimulates Sertoli cells (testes) to produce androgen binding protein (spermatogenesis). Stimulated by GnRH (gonadotroph releasing hormone) from hypothalamus
leutinizing hormone. In females stimulates ovulation, corpus luteum formation, and progesterone production. In males, stimulates Leydig cells to secrete testosterone (spermatogenesis) stimulated by GnRH (gonadotroph releasing hormone) from hypothalamus
Prolactin or mammotropin. stimulates mammary glands to produce milk, may stimulate oligodendrocyte precursor cells in CNS, high levels cause infertility in men. Inhibited by PIH (prolactin inhibiting hormone) from hypothalamus
In women, stimulates smooth muscle contraction ar birth, mammary function, and maternal bonding. In men, facilitates sperm transport and social behavior. most is produced in paraventricular nucleus. bound non convalently to transport proteins, neurophysins and ATP.
ADH (antidiuretic hormone). most is produces in supraoptic nucleus. bound non convalently to transport proteins, neurophysins and ATP.
Structure of bone
Epiphysis, Metaphysis, and Diaphysis
Three main sources of blood supply
nutrient artieries, perisoteum arteries, and metaphyseal complex
Functional organization of bone
Compact (cortical) bone and spongy (trabecular, cancellous) bone
differentiate into osteoblasts (mesychymal stem cells or multipotent marrow stromal cells)
secrete extracellular matrix of bone (osteoid) when active, cuboidal/columnar, squamous when inactive. found on all surfaces of bone
stellate cells that are surrounded by and maintain the bone matrix. come from osteoblasts. most numerous of bone cells. communicate the mechanical load and strain in the bone to guide formation/degradation.
bone-destroying cells. active when bone is being resorbed. derived from monocytes, but are multinucleated (2-50 monocytes). Can be on the inner surface (endosteal) or outer surface (periosteal).
perpendicular canals to supply blood to the osteocytes
center of an osteon, supplies blood to chondrocytes Require 3-4 months to complete
bone replacing tissue within cartilage. hyaline cartilage forms in developing embryo, mesynchymal cells differentiate into osteoprogenitor cells, and then go to osteoblasts and secrete osteoid (unmineralized, organic part of bone). The osteoid becomes mineralized, forming the bony collar that surrounds the future diaphysis. chondrocytes are cut off and mineralize as they die.
collagen I, glycosaminoglycans, proteoglycans. glycoprotein called osteocalcin binds calcium. Osteoblasta also accumulate calcium and phosphate ions to deposit hydroxapatite (mineralization)
Initiation of marrow cavity
osteogenic bud tunnels into diaphysis of calcified cartilage. It's chondroclasts followed by angiogenic bud, osteoprogenitor cells, osteoblasts, and nerves. The middle becomes the primary ossification center. Cartilage is destroyed and replaced by bony trabeculae. Cavity fills with reticular CT (III) and hematopoietic tissue from fetal liver.
secondary ossification center
osteogenic buds invade epiphyses, at birth. The intervening hyaline cartilage becomes epiphyseal plate (growth plate).
flat bones do not require cartilage model. mesynchymal cells between the skin and brain condense to form thickened sheets (membranes) of cells and ECM. responding to growth factors, some differentiate into osteoprogenitor cells and then into osteoblasts, which secrete osteoid. The osteoid becomes mineralized and then strips (plates) of bones form.
Bone length growth
Epiphyseal plate - zone of resting cartilage (nearest epiphysis, random chondrocytes), then zones of proliferation (chondrocytes division/alignment), hypertrophying (chondrocyte enlargement), and calcifying cartilage (chondrocytes die/matric minerialized), then ossification zone (calcified cartilage is resorbed by chondroclasts and bone is deposited).
Proliferation/hypertrophying contribute to bone growth.
Bone width growth
appostional growth, osteoblasts from the periosteum (dense irregular CT) add new layers of bone. Osteocytes keep contact with filopodia within canaliculi.
Exchanges nutrients/waste in between osteocytes trapped in bony matrix.
distance between two rows of osteocytes. A chain of osteocytes can only communication between 8-10 lamellae.
rows around endosteum and periosteum of long bones. don't need haversian canals.
Primary, woven bone (initial, unorganized) is destroyed and replaced by secondary bone (repeated many times). Secondary bone is stronger from greater mineralization/regularly arranged collagen.
1) incorporate new blood vessels, initiated by osteoclasts which secrete enzymes to tunnel through bone. Blood vessels follow, first perpendicular (Volksmann's canals), then parallel (Haversian).
fractued, unsalvageable fragments are resorbed by macrophages. a callus from periosteum/endosteum unites the salvageable fragments. If stabalized, little callus forms and growth = intramembraneous ossification (primary bone healing). else, hyaline and then endochondral ossification (secondary bone healing).
causes calcium deposition in bone. antagonizes PTH