Blood and Endocrinology Lab Flashcards

Practice flashcards covering blood composition, hematopoiesis, red blood cell life cycle, white blood cells, hemostasis, blood typing, and endocrine system histology and physiology.

What percentage of total blood volume is occupied by plasma and red blood cells in a centrifuged sample of blood?

Plasma accounts for $55\%$ of total blood volume, while red blood cells account for $45\%$.

What is the buffy coat in centrifuged blood composed of?

The buffy coat is a thin layer composed of white blood cells and platelets located between the plasma and red blood cells.

What are the major protein components of blood plasma and their relative percentages?

Plasma proteins make up $7\%$ of total plasma weight and consist of albumins ($54\%$), globulins ($38\%$), fibrinogen ($7\%$), and all others ($1\%$).

What are the normal numerical counts per microliter ($\mu\text{L}$) for red blood cells, white blood cells, and platelets in circulating blood?

Red blood cells: $4.8-5.4\text{ million}$ per $\mu\text{L}$; White blood cells: $5000-10,000$ per $\mu\text{L}$; Platelets: $150,000-400,000$ per $\mu\text{L}$.

Which white blood cells are classified as granular leukocytes versus agranular leukocytes, and what are their normal percentages?

Granular leukocytes include neutrophils ($60-70\%$), eosinophils ($2-4\%$), and basophils ($0.5-1.0\%$). Agranular leukocytes include lymphocytes ($20-25\%$) and monocytes ($3-8\%$).

In hematopoiesis, which progenitor cell lineages develop from myeloid stem cells versus lymphoid stem cells?

Myeloid stem cells give rise to CFU-E (erythrocytes), CFU-Meg (platelets), CFU-GM (neutrophils, eosinophils, basophils, monocytes/macrophages), and mast cells. Lymphoid stem cells give rise to T lymphoblasts (T cells), B lymphoblasts (B cells/plasma cells), and NK lymphoblasts (natural killer cells).

What is the molecular structure of hemoglobin and what gives it the ability to bind oxygen?

Hemoglobin consists of globin (two alpha and two beta polypeptide chains) and four non-protein iron-containing heme groups. Each heme group contains an iron ion ($\text{Fe}^{2+}$) that reversibly binds one oxygen molecule.

What is the average lifespan of a red blood cell, and how is globin recycled upon RBC destruction?

Red blood cells circulate for about $120\text{ days}$. Globin is broken down by macrophages into amino acids, which are reused for new protein synthesis.

What is the breakdown path of the non-iron portion of heme from macrophages to excretion?

Non-iron heme is converted to biliverdin, then to bilirubin. Bilirubin is transported to the liver, secreted into bile, and converted by intestinal bacteria to urobilinogen. Urobilinogen is either converted to stercobilin (excreted in feces) or reabsorbed into blood and converted to urobilin (excreted in urine).

What are the three sequential steps of leukocyte emigration from blood vessels into tissue?

The three steps are rolling, sticking, and squeezing between endothelial cells. Adhesion molecules involved include selectins on endothelial cells and integrins on neutrophils.

What are the three main stages of platelet plug formation in hemostasis?

1. Platelet adhesion (sticking to damaged endothelium and collagen fibers); 2. Platelet release reaction (liberating ADP, serotonin, and thromboxane $\text{A}_2$); 3. Platelet aggregation (forming a platelet plug).

What antigens are present on RBCs and what antibodies are present in plasma for each ABO blood type?

Type A: A antigen, anti-B antibody; Type B: B antigen, anti-A antibody; Type AB: Both A and B antigens, neither antibody; Type O: Neither A nor B antigen, both anti-A and anti-B antibodies.

How does Hemolytic Disease of the Newborn (HDN) develop across pregnancies in an $\text{Rh}^-$ mother?

During a first pregnancy with an $\text{Rh}^+$ fetus, $\text{Rh}^+$ fetal antigens enter mother's blood during delivery, causing her to produce anti-Rh antibodies. In a second $\text{Rh}^+$ pregnancy, these anti-Rh antibodies cross the placenta and destroy fetal red blood cells.

How do circulating hormones differ from paracrine and autocrine local hormones?

Circulating hormones are secreted into blood capillaries and travel through the bloodstream to act on distant target cells. Paracrine hormones act on nearby target cells. Autocrine hormones act on the same cell that secreted them.

What is the mechanism of action for lipid-soluble hormones inside target cells?

Lipid-soluble hormones diffuse through the lipid bilayer into the target cell, bind to intracellular receptors in cytosol or nucleus to form an activated receptor-hormone complex that alters gene expression (transcription of DNA into mRNA), leading to protein synthesis on ribosomes.

What is the signal transduction pathway for water-soluble hormones in target cells?

The water-soluble hormone (first messenger) binds to a cell surface receptor, activating a G protein, which activates adenylate cyclase. Adenylate cyclase converts ATP to cyclic AMP (cAMP, second messenger), which activates protein kinases that phosphorylate cellular proteins to produce a physiological response. Phosphodiesterase inactivates cAMP.

What vascular structure connects the hypothalamus to the anterior pituitary, and how do hypothalamic hormones travel through it?

The hypophyseal portal system connects them. Hypothalamic neurosecretory cells release releasing and inhibiting hormones into the primary plexus in the median eminence, which flow through hypophyseal portal veins to the secondary plexus in the anterior pituitary.

What five specific cell types exist in the anterior pituitary, and which hormones do they secrete?

1. Somatotrophs: secrete human growth hormone (hGH / somatotropin); 2. Thyrotrophs: secrete thyroid-stimulating hormone (TSH / thyrotropin); 3. Gonadotrophs: secrete FSH and LH; 4. Lactotrophs: secrete prolactin (PRL); 5. Corticotrophs: secrete ACTH (corticotropin) and MSH.

How do hypoglycemia and hyperglycemia regulate human growth hormone (hGH) release?

Hypoglycemia stimulates release of GHRH from the hypothalamus, which causes anterior pituitary somatotrophs to secrete hGH (raising blood glucose to normal, $\approx 90\text{ mg}/100\text{ mL}$). Hyperglycemia stimulates release of GHIH, which inhibits hGH secretion.

How is the posterior pituitary structurally connected to the hypothalamus, and which hormones are stored there?

It is connected via the hypothalamohypophyseal tract (axons of neurosecretory cells passing through the infundibulum). It stores and releases Oxytocin (OT) and Antidiuretic hormone (ADH / vasopressin).

How do hypothalamic osmoreceptors respond to high blood osmotic pressure to control ADH release and affect target organs?

High blood osmotic pressure activates hypothalamic osmoreceptors, triggering nerve impulses that release ADH from axon terminals in the posterior pituitary. ADH causes kidneys to retain water (reducing urine output), sudoriferous glands to decrease perspiration, and arterioles to constrict (increasing blood pressure).

What are the eight steps involved in thyroid hormone synthesis within thyroid follicles?

1. Iodide trapping; 2. Synthesis of TGB; 3. Oxidation of iodide ($\text{I}^- \rightarrow \text{I}_2$); 4. Iodination of tyrosine; 5. Coupling of $\text{T}_1$ and $\text{T}_2$; 6. Pinocytosis and digestion of colloid; 7. Secretion of thyroid hormones ($\text{T}_3$ and $\text{T}_4$); 8. Transport in blood bound to thyroxine-binding globulin (TBG).

What are the primary cell types in the thyroid gland and what hormones do they produce?

Follicular cells surrounding thyroid follicles synthesize triiodothyronine ($\text{T}_3$) and thyroxine ($\text{T}_4$). Parafollicular (C) cells produce calcitonin (CT).

How do calcitonin (CT) and parathyroid hormone (PTH) regulate blood calcium ($\text{Ca}^{2+}$) levels?

High blood $\text{Ca}^{2+}$ stimulates thyroid parafollicular cells to release calcitonin (CT), which inhibits osteoclasts to lower blood $\text{Ca}^{2+}$. Low blood $\text{Ca}^{2+}$ stimulates parathyroid chief cells to release PTH, which promotes $\text{Ca}^{2+}$ release from bone, decreases $\text{Ca}^{2+}$ loss in urine, and stimulates kidney release of calcitriol to increase intestinal $\text{Ca}^{2+}$ absorption.

What are the three zones of the adrenal cortex and what specific hormones does each zone secrete?

1. Zona glomerulosa: secretes mineralocorticoids, mainly aldosterone; 2. Zona fasciculata: secretes glucocorticoids, mainly cortisol; 3. Zona reticularis: secretes weak androgens, mainly dehydroepiandrosterone (DHEA).

What cell type makes up the adrenal medulla and what hormones does it secrete?

Chromaffin cells make up the adrenal medulla and secrete epinephrine and norepinephrine (NE).

What triggers the Renin-Angiotensin-Aldosterone (RAA) pathway and what are the key biochemical conversions in this pathway?

Dehydration, $\text{Na}^+$ deficiency, or hemorrhage causes decreased blood volume and blood pressure. Juxtaglomerular cells of kidneys secrete renin, which converts liver-derived angiotensinogen to angiotensin I. ACE in lungs converts angiotensin I to angiotensin II, which stimulates vasoconstriction and adrenal cortex secretion of aldosterone to increase $\text{Na}^+$ and water reabsorption.

What four cell types are present in pancreatic islets (Islets of Langerhans) and what hormone does each produce?

1. Alpha cells: secrete glucagon; 2. Beta cells: secrete insulin; 3. Delta cells: secrete somatostatin; 4. F cells: secrete pancreatic polypeptide.

How do glucagon and insulin oppositely regulate blood glucose levels?

Low blood glucose stimulates pancreatic alpha cells to secrete glucagon, which causes liver cells to convert glycogen to glucose (glycogenolysis) and form glucose from lactic acid and amino acids (gluconeogenesis). High blood glucose stimulates pancreatic beta cells to secrete insulin, which accelerates facilitated diffusion of glucose into body cells and speeds conversion of glucose to glycogen.

What are the two major phases of the stress response (General Adaptation Syndrome) and how are they initiated?

1. Fight-or-flight response: rapidly initiated by sympathetic nerves to visceral effectors and adrenal medulla (releasing epinephrine and norepinephrine); 2. Resistance reaction: a slower, longer-lasting response initiated by hypothalamic releasing hormones (CRH, GHRH, TRH) stimulating anterior pituitary secretion of ACTH, hGH, and TSH.