pathology

Topics covered: 1. Review of basics 2. Freckle (Ephelis) 3. Lentigo 4. Melanocytic Nevus (Mole) 5. Dysplastic Nevi 6. Melanoma Review of Basics: Melanocytes Melanocytes are a type of dendritic cell Melanoblasts, the precursors to melanocytes, are derived from neural crest. Wnt, expressed by the neural tube, directs neural crest cells to migrate and mature into melanoblasts.  Wnt --> binds to Frizzled, a transmembrane receptor, activating it --> this causes dissociation of GSK3beta from beta-catenin --> beta-catenin translocates to the nucleus where it binds with Tr factor to initiate MITF (microphthalmia-associated transcription factor) transcription. MITF --> important in differentiation of melanoblasts. MITF induces transcription of tyrosinase , tyrosinase-related protein-1 (TRP-1) and DOPA (aka TRP-2).  Tyrosinase (TYR gene) is responsible for the first step in melanin production , tyrosine conversion to DOPA.  Oculocutaneous albinism (OCA)  -- TYR

Definitions Neoplasia : a disorder of cell growth triggered by a series of acquired mutations affecting a single cell and its clonal prodigy. The new growth produced by these mutations is called a neoplasm .  grade : degree of differentiation of the cells stage : clinical system to help determine the prognosis of a patient with a neoplasm Tumor (T): how large is the primary tumor? Node (N): has the tumor spread to regional lymph nodes? Metastasis (M): is there distant spread (metastasis) of the tumor? Oncology : the study of tumors or neoplasms Tumor : 1. the swelling caused by inflammation, 2. new growth (i.e. neoplasm) Desmoplasia : when parenchymal cells stimulate the stroma (connective tissue, blood vessels, adaptive immune cells) become abundant and collagenous.  Angiogenesis : formation of new blood vessels to allow the tumor to grow larger.  Benign tumors : localized, can be removed with surgery, and the gross and microscopic appearance is not worrying; usuall

Posterior Pituitary gland Posterior pituitary gland (neurohypophysis)  is arises from a ventral outgrowth of the primitive hypothalamus. The posterior pituitary gland secretes two key hormones: Antidiuretic hormone (ADH) and Oxytocin.  Antidiuretic hormone (ADH) Antidiuretic hormone (ADH) , also known as vasopressin , is made by supraoptic vasopressinergic neurons. It acts at the kidney to increase the permeability of the collecting duct allowing it to reabsorb more water back into the serum. This prevents "diuresis" or dilute urine to be produced, instead the urine made is concentrated with higher osmolarity. It is produced in response to increased serum osmolarity and hypovolemia , and its production is inhibited by low serum osmolarity. ADH is very important in maintaining proper serum osmolarity.  Syndrome of inappropriate antidiuretic hormone (SIADH) : too much ADH is produced. Patients have urine with high osmolarity and serum with low osmolarity (low serum

Hyperemia = increased blood flow to tissue due to dilation of arteries.  Erythema = redness of tissues due to increased oxygen delivery Congestion = reduced drainage of blood from tissues that can occur systemically (e.g. heart failure) or locally (e.g. venous obstruction). Remember, reduced venous drainage causes back up of blood and increased hydrostatic pressure within capillaries which leads to edema. Also, because blood can not be drained from the tissues, new blood can not be effectively sent to the tissues either, leading to hypoxia which can lead to ischemia, injury, etc. If the pressure from the increased hydrostatic pressure is too much, the capillaries may rupture leading to hemorrhage, as red blood cells enter the interstitium.  cyanosis = blue-red color of tissues due to hypoxia e.g. deoxygenated hemoglobin in the red-blood cells.  acute pulmonary congestion = fluid accumulates in alveolar septa, and fluid along with red blood cells (due to capillary ruptu

About 1/3 of total body water (TBW) is outside cells (extracellular space) and about 3/4 of this is between cells (interstitial fluid), with the remaining 1/4 inside the vasculature. Terminology Edema = accumulation of fluid in tissues that is clinically noticeable. Remember, fluid stasis creates a favourable environment for bacterial growth! cerebral edema = can be diffuse or localized. As the brain swells, the gyri become distended and sulci become narrow. The brain has a fixed space in which to expand, so if the swelling progresses, it is pushed out of the cranium (herniation), often through the foramen magnum.  pulmonary edema = fluid accumulation in the lungs. The normally air-filled lungs become heavy, as the air is mixed with fluid and red blood cells from the capillaries. Fluid collects in the alveolar septa around the capillaries and in the alveolar spaces too. Fluid in the alveoli can allow for bacteria to grow leading to infection.  periorbital edema = fluid acc