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175 Cards in this Set
- Front
- Back
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main role of the urinary system
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maintain whole-body homeostasis
1. filtering blood: resorbing water and select molecules; secreting metabolites and minerals, excreting them along with water 2. maintaining acid base balance 3. regulation of electrolyte concentration 4. control of blood volume 5. regulation of blood pressure |
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define: filtration, reabsorption, and secretion
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Filtration: accomplished by the movement of fluids from the blood into the Bowman's capsule
Reabsorption: involves the selective transfer of essential solutes and water back into the blood Secretion: involves the movement of wastes from the blood into the nephron |
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renin-angiotensin/aldosterone controls what homeostatic functions?
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blood volume and pressure
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what is the origin of the urinary system?
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mostly intermediate mesoderm
Embryonic mesonephros is replaced by metanephric kidney and ureters. Begins as diffuse clusters of tissue that extends along the dorsal body wall of embryo The bladder and urethra derive from hindgut endoderm |
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structures and their functions in the urinary system
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a. filtration: highly vascularized area (GLOMERULAR CAPILLARY) with interdigitating filtrative tissue (BOWMAN'S CAPSULE VISCERA) to provide increased surface area
b. Specialized differentiated renal tubules (PCT, LOOP of HENLE, DCT) convey and process filtrate, i.e. reabsorption and secretion c. Urinary bladder: used as a sac lined with TRANSITIONAL EPITHELIUM underlying connective tissue, and smooth muscle that can relax and stretch to retain urine. |
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renal circulation path
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abdominal aorta --> Renal Artery --> Interlobar Artery --> Arcuate Artery --> Interlobular Artery --> Afferent Arteriole --> Glomerular Capillary --> Efferent Arteriole --> Peritubular Capillary Plexus/Vasa Recta --> Interlobular Vein --> Arcuate Vein --> Interlobar Vein --> Renal Vein --> Inferior Vena Cava
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nephron
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1. structural and functional unit or metanephric kidney
2. more than 1 million 3. tubules lined with simple epithelium (cuboidal, columnar) c. begin at Bowman's capsule, a blind ended sac around the glomerular capillary comprise the blood urinary interface d. afferent arteriole is under high hydrostatic pressure. provides driving force for propelling fluid efflux out of the glomerular capillary and into the interstitium before going to Bowman |
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Glomerular Filtration Rate
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Measured clinically by the renal clearance of Creatinine
GFR depends on renal capillary hydrostatic pressure, filtration selectivity, and plasma concentration of filtered substance -Renal Plasma Flow is measured clinically by clearance of PAH -GFR is~20% Renal Plasma Flow |
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Blood flow away from glomerulus via efferent arteriole can converge onto these secondary capillary beds
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Peritubular Capillary Plexus (PTCP) --> cortical and juxtamedullary nephrons
Vasa Recta (VR) --> juxtamedullary nephrons (penetrate deeper into medulla) |
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peritubular capillaries
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envelop all convoluted tubules of the cortical and juxtamedullary nephrons (proximal and distal) and play a central role in rabsorption
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vasa recta
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capillaries that serve the juxtamedullary nephrons after the PTCP. Maintain osmotic gradient in the medulla
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is the nephron a portal system?
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yes
glomerular (cap bed #1) --> efferent arteriole --> PTCP and VR (cap bed #2) |
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Bowman's capsule
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-blind ended sac that embraces glomerular capillary cluster
-located in the renal cortex -parietal layer consists of simple squamous epithelium -visceral layer (contact with glomerular capillary)is specialized with podocytes |
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podocytes
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on the visceral layer of bowman's capsule
branched pedicel that have intervening slits through which filtrate can pass connect with the arteriole |
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Proximal convoluted tubule (PCT)
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-Reabsorbs glucose, vitamins, amino acids, and other "food substances" from tubular filtraet and pass them to interstitium peritubular capillary plexus
-simple cuboidal epithelium -apical luminal side of PCT have brush border microvilli (increase surface area) -pump ions against their concentration gradients |
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Loops of Henle
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-PCT leads to a hairpin loop.
-establishes a hypertonic environment in the renal medulla -thin descending limb --> thin segment --> uturn --> thin ascending limb --> thick ascending limb -U turn comprised of simple squamous epithelium -thick ascending comprised of simple cuboidal |
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Distal convoluted tubule
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-simple cuboidal epithelium
-no microvilli -contributes the "macula densa" to JGA in the vicinity of Bowman's capsule (part of same nephron) -Hypotonic fluid reaches DCT and further Na+ reabsorption may occur (ie in response to aldosterone) -fuses with collecting tubule |
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Collecting Ducts
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visible renal medulla and lined with high cuboidal that becomes columnar epithelium as you transition from collecting tubule to collecting ducts
collecting tubules --> collecting ducts --> papillary ducts --> renal pelvis --> ureter --> bladder |
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blood-urinary filtration unit
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glomerular capillaries + bowman’s capsule
• Glomerular: Fenestrated capillaries without diaphragms and continuous basement membrane • Bowman’s Capsule: visceral layer consists of podocytes with foot processes, pedicles that encapsulate surface of glomerular capillaries. • Basement membrane is formed by basal lamina of podocyte + basal lamina of glomerular capillary endothelium |
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Filtrate
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glucose, ions, vitamins, but NOT RBC and NOT plasma proteins.
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Goodpasture Syndrome
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auto-antibodies against basement membrane basal lamina (type IV Collagen) will disrupt glomerular barrier and cause hematuria
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podocyte/endothelial interface
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Juxtaglomerular Apparatus JGA
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Made up of JG cells and Macula Densa
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JG Cells
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-specialized smooth muscle cells located within walls and later become tunica media of afferent arterioles
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Macula Densa
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area of closely packed linear array epithelial cells lining wall of DCT and adjacent to JG cells.
Senses DCT fluid osmolarity and water volume --> stimulates JG cells to secrete renin |
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renin-angiotensin-aldosterone system
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increases and maintains blood pressure
angiotensin (liver)--> converted to angiotensin I by renin (renal JG cells) --> converted to angiotensin II by converting enzyme ACE (lung) angiotensin II increases blood volume and blood pressure |
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how does angiotensin II increase blood volume?
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-stimulating aldosterone secretion by adrenal cortex (zona glomerulosa) -->increases NA+ and water reabsorption at DCT
-Vasocontriction of the arteriole increasing peripheral vascular resistance resistance, and increasing mean arterial pressure -stimulates anterior pituitary to secrete ADH vassopressin to promote increased water reabsorption at collecting ducts -stimulates sympathetic autonomics to promote vasoconstriction of peripheral vessels |
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Renin-angiotensin-aldosterone system image
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Collecting Duct
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-anti-diuretic hormone (vasopressin) induces upregulation of aqua porins which are water transport channels to increase water permeability and concentrate urine
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what is the driving force for water reabsorption in the collecting duct?
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hypertonic renal medullary interstitium, which is established by long Loops of Henle (juxtamedullary nephrons).
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urters
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•Collecting duct converge on ureters
•Tubes with thick muscular walls and are lined by transitional epithelium. Muscle layer is reversed: so inner longitudinal and outer circular |
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urinary bladder
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•Thick muscular wall with transitional epithelium.
•Occluding Junctions (Tight) •Little urine = relaxed, so surface cells are bulging and appear fuller. •A lot of urine = stretched, so surface appear stratified layers |
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excretory duct slide
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urinary bladder slide
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negative feedback
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•Key regulatory mechanism of endocrine system: end product inhibits upstream enzyme or releasing hormone secretion.
Example: ACTH inhibits both ACTH releasing hormone in hypothalamus and ACTH synthesis in adrenal cortex. •Maintains hormonal homeostasis: hormone levels within appropriate physiological range |
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positive feedback
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•regulatory mechanism, less common. End product stimulates hormone secretion chain.
ex: uterine contraction and lactation (milk secretion), both under oxytocin regulation. |
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overview of pituitary
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-Located at base of brain.
-2 Halves: Anterior Pituitary (adenohypophysis) and Posterior Pituitary (Neurohypophysis) •AP develops from Rathke’s pouch which emerges from roof of embryonic mouth. •PP develops from floor of diencephalon (hypothalamus), which gives rise to infundibulum (stalk) and continues as pars nervosa. |
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4. Pituitary Portal System (AP Adenohypophysis)
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a. Portal system between two adjacent capillary beds of hypothalamus and AP
b. Hypothalamus secret releasing hormones/factors and inhibitors • Influence synthesis and secretion activity of AP. • Produced by neurons in hypothalamus, secreted in capillary bed there, and travel via portal vessels to AP. |
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does the posterior pituitary have a portal system? Why or why not?
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PP does NOT have a portal system.
Why NOT? PP contains dilated ends of terminal axon bouton, herring body, whose neuronal cell body reside within hypothalamus. |
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pituitary detail image
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5. Anterior Pituitary
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a. Epithelial endocrine cells with coiled cords surrounded by vascularized connective tissue
b. Types of cells identified by staining characteristics •Chromophobes: pale degranulated chromophils or undifferentiated cells •Acidophils: Growth Hormone (GH) and Prolactin •Basophils: FSH, LH, ACTH, TSH Acronym: F.L.A.T. |
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boundary between anterior and posterior pituitary
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Growth Hormone
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a. Stimulates growth indirectly by acting as insulin-like growth factor on epiphyseal plates
b. Promotes both endochondral and intramembranous ossification c. Promotes bone mineral deposition and elongation d. Promotes skeletal muscle growth |
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Excess GH in children vs adults
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e. Excess GH in adults lead to acromegaly (after fusion of epiphyses) → coarse facial futures
f. Excess GH in children, gigantism (prior to fusion of epiphyses) → growth plates still present |
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Insufficient GH
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Hypopituitary Dwarfism
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Prolactin
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a. Stimulates milk synthesis by mammary glands’ lactiferous alveoli.
b. Oxytocin induces milk secretion by lactiferous ducts. c. Regulated via positive feedback. |
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ACTH (adrenocorticotropic hormone):
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stimulates adrenal cortex to produce steroid hormones such as cortisol and aldosterone
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TSH (Thyroid stimulating hormone)
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stimulates thyroid gland to synthesize and secrete thyroid hormone thyroidglobulin, which is iodinated into active form thyroxine: T3,T4
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Gonadotropins: target ovaries and testes
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FSH (Follicle stimulating hormone): stimulates follicle development in the ovary and spermatogenesis in the testes
LH LH (Leutinizing Hormone) --female version: Ovulation, development of corpus luteum, and stimulates progesterone secretion ICSH (Interstitial Cell Stimulating Hormone--male version): testosterone secretion by Leydig cells |
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AP basophil hormones
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PP hormone diagram
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Posterior Pituitary
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a. Derived from neuro-ectoderm. Contains unmyelinated axons of secretory nerve cells.
b. Cell bodies reside in hypothalamus and neuronal axons extend into PP. Hormones are stored in Herring bodies, which are dilated axonal endings in PP. c. Hormones, which are really neurotransmitters but act as hormones d. vasopressin (ADH) and oxytocin |
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Vasopressin (ADH)
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•Promotes vascular smooth muscle (tunica media) contraction = vasoconstriction → increase blood pressure
•Increases water permeability of collecting tubules and ducts → reabsorb water into hyperosmotic medullary interstitium to maintain blood volume and pressure |
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• Oxytocin
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•Promotes uterine contractions and lactiferous gland and duct secretion
•Operates via Positive feedback. Critical for labor and lactation |
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Posterior pituitary histo slide
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Thyroid origin
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endodermal, epithelial bud from floor of oral cavity foramen cecum.
primordial bud migrates distally and becomes situated ventral to upper trachea |
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structure and location of thyroid
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Double-lobed gland spanning laryngo-tracheal region
Simple cuboidal epithelium-lined follicles, connective tissue and interstitium |
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thyroid hormone activity
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Hormone secretion controlled by autonomic nerves and by pituitary TSH
follicular cells secrete thyroglobulin or colloid which is stored in follicle interior → iodine then combines with these precursor molecules and prepared to be secreted basally as active T3 (tri-iodothyronine) or T4 (thyroxine) Follicular cells secrete thyroglobulin apically into follicular lumen, but T3 and T4 are secreted basally Stores appreciable amount of its product in an inactive form |
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T3 and T4 regulate what?
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BMR (Basal Metabolic Rate) aka oxidative cellular respiration, and proportional to rate of oxygen consumption.
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thyroid slide
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Thyroid summary slide
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iodine and thyroid
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Goiter
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refers to enlargement of the thyroid gland. Due to either hypo- or hyper-thyroidism
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Hypothyroidism
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Iodine Deficiency → can’t produce iodinated hormone → reduce BMR → sluggish, weight gain
•Cretinism: severely stunted physical and mental growth due to untreated deficiency of thyroid hormone •Hashimoto’s: autoimmune condition •Myxedema: thickened, non-pitting edematous changes to soft tissues of patients in markedly and prolonged hypothyroid state. Accumulate mucopolysaccharides “myxedema” which is reversible with thyroid hormone therapy |
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Hyperthyroidism
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•Graves’ Disease: autoimmune disease, in which auto-antibodies are directed against TSH-receptors, that constitutively and chronically stimulate the receptor, thereby resulting in overproduction of thyroid hormones, hence hyperthyroidism
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Thyroid Parafollicular Cells
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C-cells appear in clusters and make Calcitonin, which inhibits bone resorption and reduces serum calcium through inhibiting osteoclast activity
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Parathyroid Gland
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a. Endodermal Epithelium, pharyngeal pouches 3 & 4
b. 4 pea-sized parathyroids embedded in dorsal side of thyroid gland c. Functional Parenchyma consists of cords of secretory cells supported by reticular matrix CHIEF CELLS AND OXYPHILS |
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Chief cells
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•make PTH (parathyroid hormone), which increases blood calcium and decreases blood phosphate → normal neuromuscular activity
•Promote bone resorption by osteoclasts (indirectly) via a factor produced by osteoblasts •Hyperparathyroidism ⇒ high blood calcium and low phosphate |
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Oxyphils
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larger and more acidophilic (stain more eosinophilic). Unknown function
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parathyroid image
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adrenal gland
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Epithelial cortex and neural-crest derived medulla
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3 zones of the adrenal cortex
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Zona Glomerulosa
Zona Fasciculata Zona Reticularis |
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Zona Glomerulosa
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o Synthesizes mineralcorticoids aldosterone → DCT to reabsorb Na+ and water.
o Stimulated by Angiotensin II and ACTH o Cells arranged in clusters |
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Zona Fasciculata
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o Synthesizes glucocorticoids cortisol affect carbohydrate metabolism.
o Anabolic action on liver to promote enzyme (protein) synthesis, gluconeogenesis, and glycogen synthesis. o Catabolic outside liver to promote proteinolysis and lipolysis. o Cells are arranged in parallel bundles o Stimulated by Corticotropin (ACTH) |
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Zona Reticularis
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o Synthesizes androgens (masculinizing hormones; 17-ketosteroids)
o Stimulated by ACTH |
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adrenal cortex disorders
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note: adrenal cortex exhibits negative feedback
• Cushing’s syndrome: adrenal cortical hyperfunction → prolonged elevated cortisol levels ⇒ central obesity, moon fascies, weight gain, excess sweating • Addison’s Disease: hypofunction in all 3 zones → chronic adrenal insufficiency → Hyposmotic Volume Contraction |
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Adrenal medulla
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• Consists of modified postganglionic neurons that receive presynaptic sympathetic innervation
• Produces catecholamines: epinephrine (adrenaline) and norepinephrine (noradrenaline) for sympathetic effects “fight or flight” • “Sympathetic ganglion” With preganglionic fibers impinging on post-ganglionic cell bodies (reside in medulla) with no axons |
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adrenal medula histo slide
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Stroma of sinusoids support parenchyma chromaffin cells which are modified postganglionic sympathetic neuron. Stimulated by Acetylcholine and produces Neurohormone that enters blood.
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adrenal medulla overview pic
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Pancreas (endocrine)
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Islets of Langerhans: Clusters of endocrine cells among exocrine acinar cells
• Endoderm-derived. Islets consists of cords and sinusoidal capillaries Beta and Alpha cells |
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Beta-cells
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secrete polypeptide insulin that lowers blood glucose and promote increased glucose uptake by liver and skeletal muscle. Stimulates Anabolism
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Alpha-cells
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secrete glucagon that increases blood glucose by stimulating counter-regulatory effects: gluconeogenesis, glycogenolysis
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pancreas endocrine hormones
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insulin
glucagon somatostatin (inhibits both beta and alpha cells) pancreatic polypeptide |
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islets of langerhans
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Diabetes
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• Type 1 diabetes: Destruction of beta islet insulin making cells (no insulin)
• Type 2 diabetes: Insufficient insulin or it cannot be used properly (insulin resistance) |
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Pineal Gland: “third eye”
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a. Diverticulum outpouching of brain: pinealocytes make melatonin, which is released according to light/dark stimuli via fibers relaying form optic cortex
b. Melatonin is associated with regulating circadian rhythm. |
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pineal gland histo
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Mitosis
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•One cell division
•Diploid (2n) → diploid (2n) •Results in 2 daughter cells, genetically identical to parent cell |
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Meiosis
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•Two cell divisions
•Diploid (2n) → haploid (1n) •Results in 4 daughter cells, each with ½ the genetic material of the parent + some variation due to crossing over |
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Review of Mitosis and Meiosis
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teste origin
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Gonad (testes) and ducts arise from intermediate mesoderm
• Specifically come from the gonadal/genital ridge area • Gonads provide housing for primordial germ cells (PGCs) and serve as endocrine structures • PGCs migrate from an outpouching of the dorsal mesentery (near the gut tube) to the genital ridge (see diagram below) • PGCs in testes → mature into sperm cells |
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male reproductive tube origins
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Efferent ducts, epididymis, and vas deferens derived from mesonephric tubules
• Branching of the ducts produces various endocrine glands |
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Gonads (Testis):
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site for gametogenesis/ endocrine function
• Composed of Seminiferous tubules embedded in a connective tissue interstitium • Sertoli cells: epithelial cells lining the tubules • Leydig cells: found in the interstitium • PGCs are found in the seminiferous tubules → sandwiched between Sertoli cells |
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teste diagram
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Male Tubes & Ducts Route
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convey gametes
• Seminiferous tubule → Straight Tubule → Rete Testis → Efferent Ducts → Epididymis → Vas Deferens → Ejaculatory Duct → Urethra • Vas Deferens called “ejaculatory duct” after it passes through the seminal vesicles •Associated glands: seminal vesicle, prostate gland • Develop as diverticulum of ducts |
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Endocrine influences on the testes
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hypothalamic-pituitary axis
a. Interstitial Cell Stimulating Hormone (ICSH) from the pituitary targets Leydig cells • Produces Testosterone → supports spermatogenesis & secondary sex characteristics b. FSH from pituitary targets Sertoli Cells • Produces Androgen Binding Protein (ABP) • Binds testosterone from the interstitium and concentrates it within the seminiferous tubules, where spermatogenesis occurs |
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Androgen Insensitivity Syndrome
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• Testosterone manufactured, but receptors defective.
• Testes are formed, but undescended, and phenotypically female characteristics appear |
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Spermatogenesis summary
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Spermatogonia (2n, 2c) → Primary Spermatocyte (2n, 4c) → Finishes Meiosis I → Secondary Spermatocytes (N, 2C) → Finishes Meiosis II → Spermatids (N, C)
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Spermatogonia (2n, 2c)
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PGCs that migrate to the gonadal ridge from dorsal mesentery
• Located in seminiferous tubules; most “immature” step in spermatogenesis • Divide through mitosis → at puberty, some enter meiosis I, forming primary spermatocyte |
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Primary Spermatocyte (2n, 4c)
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have 2x the DNA as spermatogonia, but same # of chromosomes
• Finish meiosis I to form two Secondary Spermatocytes (N, 2C). • Secondary Spermatocytes complete Meiosis II to form haploid Spermatids (N, C). |
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spermatogenesis slide
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Sertoli cells
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long, columnar epithelial cells → line the seminiferous tubule
Spermatogonia and spermatocytes live in between the sertoli cells • Produce ABP to concentrate testosterone within tubules • Produce AMH → Mullerian ducts degenerate • Engulf excess cytoplasm from forming spermatozoa (residual bodies) |
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Blood seminiferous Barrier
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“Belt” formed by tight junctions between sertoli cells
• Separates spermatogonia from primary spermatocytes → divides the tubules into a “basal” and “adluminal” compartment (see diagram above) • Prevents immune response to primary spermatocytes |
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Leydig cells
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produce testosterone
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spermiogenesis process overview
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• Microtubules from microtubule-organizing center (MTOC) lengthen to form flagella on basal body
• Mitochondrial “sheath” forms around flagellum (provides ATP for motility) • Acrosome “cap” forms around the nucleus → contains acrosomal enzymes • Excess cytoplasm (residual body) is shed → engulfed by Sertoli cells |
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Rete Testis
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“Network” of ducts → help concentrate sperm before they enter epididymis by absorbing excess fluid
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Efferent Ducts
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Connect rete testis with epididymis
• Composed of columnar epithelium: • Mix of both ciliated and non-ciliated (absorptive) cells → produces “scalloped lumen” • Only ducts in this system with “real” cilia • Smooth muscle layer surrounding epithelium |
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Epididymis
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Store and mature sperm
• Lined with pseudostratified epithelium with stereocilia • Not real cilia because they aren’t motile |
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Vas Deferens
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• Looks very similar to epididymis: also contains pseudostratified columnar epithelium with stereocilia
• Contains thick, circular smooth muscle wall to propel sperm |
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Seminal Vesicles
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Produces seminal fluid
• Diverticulum of the vas deferens • Covered by CT • Lumen is confluent with that of the vas. • Histologically → coiled tubules, lined with columnar epithelium |
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Prostate
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Synthesizes and secretes prostatic fluid
• Single, midline gland, lies inferior to bladder • Ejaculatory ducts enter prostate, where they meet with urethra • Urethra then brings urine or ejaculate from prostate → penis • Concretions: cysts within channels due to accumulation of fluid • Benign, non-malignant consequence of aging → causes enlargement of prostate |
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Penis: Erectile Tissue
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consisting of three venous sinusoids:
• Corpus Spongiosum: surrounds the urethra • 1 Pair of Corpus Cavernosa: surrounds the central arteries • Tunica Albuginea separates the two corpus cavernosas. • Skin: stratified squamous epithelium |
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female and male meiosis
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a. Male: product of meiosis = 4 spermatids of equal size and amount of cytoplasm
b. Female: Meiosis is arrested at two stopping points. • Stopped at Prophase I and at Metaphase II (more on this late) • Distribution of cytoplasm is unequal • Product is 1 large oocyte with the majority of cytoplasm + 3 tiny “polar bodies” • Most cytoplasm in the zygote comes from egg |
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female reproductive system origins
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Origin: derived from the genital crest in the intermediate mesoderm
•Primordial Germ Cells (PGCs) travel to crest from the dorsal mesentery •PGCs live in follicles: balls of cells that “embrace” the PGC a. At “indifferent stage”: see both Wolffian (mesonephric) and Mullerian (paramesonephric) duct • Wolffian ducts disintegrate & Mullerian ducts develop into: Fallopian tubes, uterus, cervix, and vagina. |
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function of ovaries
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House developing oocytes → site of oogenesis
housed within primordial follicles • Follicles lined with simple squamous epithelium • The oogonia will eventually develop into oocytes |
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Oogenesis
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maturation process for both follicles and oocytes
• Oogonia enters meiosis immediately→ arrested in Prophase I as primary oocytes • Primary oocytes haven’t undergone first meiotic division • Primary oocytes enlarge (hypertrophy) → Accumulate yolk in the cytoplasm • Primordial follicles also enlarge → become primary follicle → epithelium changes from simple squamous to stratified cuboidal • During puberty, one primary oocyte finishes meiosis I → becomes secondary oocyte → housed in a mature/graafian follicle • Secondary oocyte is released from the ovary during ovulation • Arrested in Metaphase II until fertilization |
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Oogenesis
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Atresia of follicles
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Process resulting in death of ¾ embryonic follicles
• go from ~2 million follicles in embryonic ovary → 500,000 follicles at birth • Continues throughout life; increases post-menopause |
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Ovarian structure
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•Ovarian surface is not a CT capsule; instead covered by germinal epithelium
Stroma/ Theca interna: interstitial cells (analogous to Leydig cells) located between the follicles •Produce estrogen under FSH stimulation ovarian follicles Also produce estrogen under FSH stimulation |
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primordial follicles
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Primordial follicles: reside on “cortical” surface → most superficial
•Simple squamous epithelium |
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Primary follicles
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•Lack of antrum (fluid-filled chamber)
•Follicular/Granulosa cells form stratified cuboidal epithelium --> Contains primary oocyte |
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Secondary follicle
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• Shows the beginning of antrum
• Also contains primary oocyte (slightly larger than in primary follicles because of yolk accumulation) |
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Tertiary/Graafian follicle
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• Single large antrum (filled with follicular fluid)
• Contains secondary oocyte • Bursts during ovulation → oocyte leaves along with corona radiata & zona pellucida |
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corona radiata
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first layer of granulosa cells → closest to oocyte
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zona pellucida
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acellular region surrounding the oocyte
• located between oocyte & corona radiata • Sperm needs to penetrate zona & corona to fertilize egg |
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Corpus Luteum
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Post-ovulatory structure formed by theca cells and granulosa cells
• Hormonal feedback: increase of LH causes ovulation → oocyte leaves follicle → follicle turns into corpus luteum, sustained by LH → corpus luteum produces estrogen and progesterone • Estrogen & progesterone from corpus luteum, granulosa cells, and theca interna helps maintain uterine lining •If fertilization does not occur, LH decreases → corpus luteum breaks down → forms corpus albicans (“scar” tissue) |
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Corpus luteum
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corpus albicans
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Oviduct (Fallopian tube)
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Where secondary oocyte travels after ovulation
Where fertilization occurs . Forms Fimbriae : Finger-like projections that open up beside the ovary • Eggs are “swept” into oviducts via ciliary movements of fimbriae. • Fallopian tube histology: no villae • Muscular wall and simple epithelium |
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phases of the menstrual cycle
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Follicular phase
Ovulation Luteal Phase |
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Follicular Phase
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(Pre-Ovulatory):Days 1-14
•Hypothalamus releases GnRH → Stimulates Anterior Pituitary to release FSH→ travels to ovary, stimulates follicle growth → granulosa cells, theca interna cells release estrogen → promotes endometrial growth |
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Ovulation
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Day 14
•Pituitary releases LH → promotes ovulation |
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Luteal Phase
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(Post-Ovulatory): Days 14-28
• High LH levels → promotes corpus luteum in ovary → CL releases progesterone, estrogen → stimulates further endometrial growth • If fertilization doesn’t occur, negative feedback from estrogen/progesterone causes decrease in LH → corpus luteum disintegrates → progesterone and estrogen decreases → endometrium & vessels slough off in menstruation |
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Uterus layers
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Endometrium: Glandular epithelium & CT (similar to a mucosa layer)
• Simple columnar epithelium Myometrium: Muscle layer • Serosa: over superior organ surface • Adventitia: inferior organ surface |
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Three phases of the uterus
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• Proliferative Phase (Days 7-14)
• Secretory Phase (days 14-28) • Menstrual Phase (Days 1-7) |
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Proliferative Phase (Days 7-14)
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•Glands and vessels appear less coiled and engorged
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Secretory Phase (days 14-28)
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•Glands and blood vessels are coiled and engorged
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•Menstrual Phase (Days 1-7)
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•“Shed, broken, bloody tissue”
•Endometrial gland and coiled blood vessels are shed Only stratum basalis is left behind → begins new growth cycle |
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Cervix
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Junction between uterus & vagina
• See epithelium transitioning from endometrial → vaginal • Endometrial side: Simple columnar with lots of invaginations & glands • Vaginal side: no glands, stratified squamous |
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Nabothian Cysts
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mucus-filled cyst in cervix, usually from build-up in the glands
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implantation
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• Fertilization occurs in the fallopian tube,
• Implantation occurs in the endometrium |
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Implanting embryo includes
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inner cell mass: embryonic body
trophoblast: extraembyonic tissue that implants and forms fetal placenta |
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trophoblast components
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•Syncytiotrophoblast: Leading edge of trophoblast. Secretes enzymes & HCG hormone → maintains corpus luteum & uterine wall
•Chorionic villi: branches of the chorion that “root” into endometrium & are bathed by maternal blood •Syncytiotrophoblast is the epithelium covering the chorionic villi |
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Placenta
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Maternal -fetal interface. Consists of:
• Chorion: Fetal side • Decidua: Maternal side → endometrium during secretory phase •Chorionic villi are found between chorion and decidua •Fetal & maternal blood do not mix. •Fetal side has unique amniotic epithelium |
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placenta fetal side
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placenta maternal side
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Mammary gland structure
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•Each breast has 15-20 lobes of branched, alveolar glands
•Glands all converge on the nipple •Each lobe associated with a single duct → lactiferous duct •Connective tissue separates tissue •Suspensory ligament: CT that connects with dermis |
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Pregnancy & Lactation
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Non-pregnancy: Duct system inactive, see very few glands
During pregnancy: Lactiferous ducts branch • Alveoli at ends of ducts proliferate (“bloom”) • Stimulated by oxytocin and prolactin Lactating:Milk accumulates in alveolar lumen |
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Resting mammary
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lactating mammary
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Integument
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skin + specialized structures (hair, nails, glands)
o Skin = largest body organ o Functions: barrier (wear/tear, infection, UV rad), homeostatic (hydration, thermoregulation), excretory (sebum/sweat), sensory (receptors for environment) |
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skin layers
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Skin Origin
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periderm (“plastic wrap”)= initial superficial layer from primordial single-cell-layered epidermis (eventually sloughed → amniotic fluid after differentiation of underlying layers)
Ectoderm → surface epidermis, hair, associated glands Somatic mesoderm → underlying CT of dermis + hypodermis Neural crest cells migrate to forming epidermis → specialized sensory endings |
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Epidermis
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stratified squamous epithelium (think protection)
5 Strata (deep → superficial): basale → spinosum → granulosum → lucidum → corneum Think: base → spiny → grainy → lucid (clear) → hard/tough Cells: keratinocytes (majority), melanocytes, Langerhans cells (APCs: immune response) |
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Stratum Basale (germinativum):
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basal renewal layer (renewed every 15-130 days)
• Considered "stem cells" of epidermis = undifferentiated, proliferating, and creating daughter cells that migrate upward → differentiatio |
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Stratum Spinosum
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cuboidal cells with spiny processes filled tonofilament bundles
•“Spines” form intercellular bridges which help form cohesion responsible for the mech strength of epidermis (and resist shear forces) •Many desmosomes present → “prickly” cell appearance •Keratinization begins |
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Pemphigus vulgaris
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Intercellular bridges “loosened/severed” → easier sloughing of superficial layer under external force (= positive Nikolsky sign = fluid-filled blister)
•Possibly due to antibodies against desmosome |
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Stratum Granulosum
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layers of flattened, granule-filled squamous cells (mostly)
•Approx 2-5 cells thick which begin flattening Cells contain: o Keratohyalin granules (with tonofilament “binders”) → keratinization o Membrane-coating granules (secretory vesicles with GAGS/lipids which have sealing, anti-dessicant effects) → supple/moist skin NOTE: burn victims lose this layer → ↑ risk of dehydration |
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Stratum Lucidum
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thin layer of flattened cells consisting mainly of sacs of densely-packed filaments
•No organelles or nuclei present •Almost translucent, found ONLY in thick skin |
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Stratum Corneum
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15-20 layers of non-nucleated/keratinized (dead) cells
•Filled with keratin composing tonofilament matrix •Tonofilaments “agglutinated” by keratohyalin granules |
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skin pigmentation
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Keratinocyte nuclei shielded from UV radiation by melanin from melanocytes
Epidermal Melanin Unit: melanocyte + keratinocyte •Tyrosine → (Tyrosinase) → Melanin NOTE: Melanocytes located in stratum basale and hair follicles! ALSO NOTE: Pigmentation NOT due predominantly to # melanocytes; instead, RATE OF MELANIN PRODUCTION (genetically-determined) |
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melanocytes
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skin tanning
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UVA (320-400nm) → melanin photo-oxidation → darkening
UVB (280-320 nm) → ↑ melanin production → “delayed tanning” |
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Albinism
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congenital disorder affecting all vertebrates → partial or complete absence of melanin (therefore pigment) in skin, hair, eyes
•Due to absence/defect in tyrosinase (ex: mutated TYR gene) |
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Vitiligo
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destruction of melanocytes → irregularly-shaped white patches on skin
•Most widely-accepted theory: autoimmune disease (possibly due to cytokines) •Other theory: self-destruction of melanocytes |
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Melanoma
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uncontrolled growth of melanocytes
•Responsible for 75% of all deaths associated with skin cancer •ABCD = Asymmetry, Borders, Color, Diameter NOTE: moles = benign collection of melanocytes |
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dermis
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CT layer subjacent to epidermis
Basal lamina follows contour of dermal papillae • Dermal papillae + epidermal peg → rete apparatus → fingerprints Two indistinct layers: papillary (closer to surface) + reticular (deeper, target for injections) |
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thermoregulation and skin
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To keep warm:
• Hypodermal insulating layer of adipose • Epidermal insulating layer of hair • Blood vessel vasoconstriction → ↓ blood flow To keep cool: • Sweat (protein secretion) from coiled tubular sweat glands → evaporative cooling • Blood vessel vasodilation → ↑ blood flow |
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classification of exocrine glands of skin
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eccrine sweat gland
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most sweat glands (don’t lose cytoplasmic components during secretions)
• Simple coiled tubular glands producing water, salt, urea, NH3, uric acid • At border between dermis/hypodermis |
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Apocrine
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specialized sweat glands in axilla/groin (pieces of gland cells break/are secreted)
• Larger lumen than eccrine, with ducts that DON’T open to skin surface • Instead, viscous fluid with (smelly) bacterial decomposition → upper hair follicles • Pheromone-related: inactive until puberty (sex hormone/epinephrine-influenced |
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Sebaceous Gland
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small skin gland secreting holocrine sebum (oily, waxy matter composed of cholesterol, triglycerides, and waxes) → hair follicles to lubricate skin & hair
•Found mostly on face/scalp though found throughout body (EXCEPT palms) •Secretions influenced by sex hormones |
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acne
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Sebum + dead skin cell + bacterial accumulation → clogged hair follicle → inflammation
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nerve supply in skin
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varying types of nerve endings → sensory receptors (mechanoreceptors, thermoreceptors, and nociceptors (pain)
focus: Meissner's corpuscles and Pacinian corpuscles |
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Meissner’s corpuscles
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mechanoreceptors for fine touch located in dermal papillae
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Pacinian corpuscles
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mechanoreceptors detecting pressure, vibration, & deep touch located deep in dermis/hypodermis
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Hair
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terminal portion = bulb + dermal papilla (with vital capillary network)
o Hair grows from the germinativum (basal) layer o Internal/external root sheaths continuous with epidermis NOTE: arector pili smooth muscle @ base contracts and stands hair ( → goose bumps) |
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skin overview
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