Anatomy and Physiology II: Endocrine and Reproductive Systems

Comprehensive vocabulary flashcards covering Chapter 18 (The Endocrine System) and Chapter 28 (The Reproductive Systems) for BIOS 204 Anatomy & Physiology II.

Endocrine Glands

Glands that secrete hormones directly into interstitial fluid (without ducts), which then diffuse into blood capillaries to be carried to distant target cells.

Exocrine Glands

Glands that secrete non-hormone products into ducts that carry secretions into body cavities, organ lumens, or the outer surface of the body.

Paracrine Hormones

Local hormones that act on neighboring target cells near the site of secretion without entering the bloodstream.

Autocrine Hormones

Local hormones that act on the same cell that secreted them.

Lipid-Soluble Hormones

Hormones—including steroids, thyroid hormones ($T_3$ and $T_4$), and nitric oxide—that circulate bound to transport proteins and diffuse directly through target cell lipid membranes to bind intracellular receptors.

Water-Soluble Hormones

Hormones—including amines, peptide/protein hormones, and eicosanoids—that circulate in a free form in blood plasma and bind to cell-surface plasma membrane receptors to activate second messenger systems like cAMP.

Permissive Effect

A hormonal interaction in which the action of a second hormone is required to enhance the responsiveness or effect of the first hormone.

Synergistic Effect

A hormonal interaction in which two or more hormones work together to produce a combined effect greater than the sum of their individual effects.

Antagonistic Effect

A hormonal interaction in which one hormone opposes the actions of another hormone.

Infundibulum

The stalk-like structure connecting the hypothalamus of the brain to the pituitary gland.

Hypophyseal Portal System

A system of blood vessels carrying hypothalamic releasing and inhibiting hormones from the median eminence of the hypothalamus directly to the anterior pituitary gland.

Somatotrophs

Anterior pituitary cells that secrete human Growth Hormone (hGH) to promote tissue growth via insulin-like growth factors (IGFs).

Thyrotrophs

Anterior pituitary cells that secrete Thyroid-Stimulating Hormone (TSH) to control thyroid gland hormone synthesis and secretion.

Gonadotrophs

Anterior pituitary cells that secrete Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH) to regulate gonadal function.

Lactotrophs

Anterior pituitary cells that secrete Prolactin (PRL) to promote milk production by the mammary glands.

Corticotrophs

Anterior pituitary cells that secrete Adrenocorticotropic Hormone (ACTH) and Melanocyte-Stimulating Hormone (MSH).

Hypothalamic-Hypophyseal Tract

A bundle of neurosecretory cell axons extending from the paraventricular and supraoptic nuclei of the hypothalamus down through the infundibulum to store and release Oxytocin and Antidiuretic Hormone (ADH) in the posterior pituitary.

Oxytocin (OT)

A hypothalamic hormone stored in the posterior pituitary that enhances uterine smooth muscle contractions during childbirth and stimulates milk ejection ("let down") from mammary glands.

Antidiuretic Hormone (ADH)

Also known as vasopressin, a hormone produced in the hypothalamus and released by the posterior pituitary that conserves body water by decreasing urine volume, reducing perspiration, and constricting arterioles to elevate blood pressure.

Thyroid Follicles

Microscopic spherical sacs surrounded by follicular cells that synthesize, store (as colloid in thyroglobulin), and secrete triiodothyronine ($T_3$) and thyroxine ($T_4$).

Parafollicular Cells (C Cells)

Cells located between thyroid follicles that secrete Calcitonin to lower blood calcium levels by inhibiting osteoclast activity.

Parathyroid Hormone (PTH)

A hormone secreted by chief cells of the parathyroid glands that increases blood calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$) levels by stimulating osteoclast activity, enhancing kidney calcium reabsorption, and promoting calcitriol synthesis.

Zona Glomerulosa

The outer layer of the adrenal cortex that secretes mineralocorticoids, primarily Aldosterone, to regulate sodium and potassium homeostasis and blood pressure.

Zona Fasciculata

The middle and widest layer of the adrenal cortex that secretes glucocorticoids, mainly Cortisol, to regulate glucose metabolism, protein breakdown, lipolysis, and anti-inflammatory responses.

Zona Reticularis

The inner layer of the adrenal cortex that secretes weak adrenal androgens, primarily dehydroepiandrosterone (DHEA).

Chromaffin Cells

Hormone-secreting cells in the adrenal medulla innervated by sympathetic preganglionic neurons that produce Epinephrine ($80\%$) and Norepinephrine ($20\%$) to intensify "fight-or-flight" stress responses.

Pancreatic Islets (Islets of Langerhans)

Endocrine cell clusters in the pancreas containing Alpha cells (producing Glucagon), Beta cells (producing Insulin), Delta cells (producing Somatostatin), and F cells (producing Pancreatic Polypeptide).

Melatonin

An amine hormone secreted by the pineal gland in response to darkness that contributes to setting the body's biological clock and circadian rhythms.

Stress Response Stages

The three sequential stages controlled by the hypothalamus in response to stressors: fight-or-flight response (sympathetic activation), resistance reaction (hormonal release of CRH, GHRH, TRH), and exhaustion (prolonged depletion leading to muscle wasting and immune failure).

Acromegaly

An endocrine disorder caused by hypersecretion of human Growth Hormone (hGH) during adulthood.

Dartos Muscle

A subcutaneous smooth muscle layer in the scrotum that contracts to wrinkle the scrotal skin and reduce heat loss.

Cremaster Muscle

Skeletal muscle fibers extending from the internal oblique muscle that elevate or lower the testes within the scrotum to maintain optimal temperature for spermatogenesis ($2\text{--}3\,^\circ\text{C}$ below body temperature).

Tunica Vaginalis

A serous membrane derived from the peritoneum that partially covers the testis, consisting of parietal and visceral layers.

Tunica Albuginea

A dense white fibrous capsule surrounding the testis that extends inward to form septa dividing the testis into internal lobules.

Spermatogenesis

The process occurring in the seminiferous tubules by which diploid ($2n$) spermatogonia undergo mitosis and meiosis to produce haploid ($1n$) spermatozoa.

Sustentacular (Sertoli) Cells

Supporting cells lining the seminiferous tubules that protect, nourish, and nourish developing spermatogenic cells, form the blood-testis barrier, and secrete androgen-binding protein (ABP) and Inhibin.

Interstitial (Leydig) Cells

Endocrine cells located in the spaces between adjacent seminiferous tubules that secrete Testosterone in response to Luteinizing Hormone (LH).

Acrosome

A cap-like vesicle covering the anterior head of a mature sperm cell containing enzymes that aid in penetrating a secondary oocyte during fertilization.

Epididymis

A comma-shaped organ along the posterior border of each testis containing a tightly coiled ductus epididymis where sperm undergo maturation to acquire motility and fertilizing capability.

Ductus (Vas) Deferens

A muscular duct that conveys sperm from the tail of the epididymis through the spermatic cord into the pelvic cavity towards the ejaculatory duct.

Ejaculatory Ducts

Short ducts formed by the union of the seminal vesicle duct and the ampulla of the ductus deferens that pass through the prostate to eject sperm and seminal fluid into the prostatic urethra.

Seminal Vesicles

Paired accessory glands posterior to the urinary bladder that secrete an alkaline, fructose-rich fluid comprising about $60\%$ of semen volume.

Prostate

A single doughnut-shaped gland surrounding the prostatic urethra that secretes a milky, slightly acidic fluid containing citric acid and proteolytic enzymes into the urethra.

Bulbourethral (Cowper's) Glands

Paired pea-sized glands located inferior to the prostate that secrete an alkaline fluid during sexual arousal to neutralize urethral acids and lubricate the glans penis.

Corpora Cavernosa Penis

The two dorsolateral masses of erectile tissue running along the body of the penis that fill with blood during an erection.

Corpus Spongiosum Penis

The midventral mass of erectile tissue containing the spongy (penile) urethra that remains pliable during erection to keep the urethra open.

Primordial Follicle

An ovarian follicle consisting of a primary oocyte surrounded by a single layer of flat follicular cells.

Mature (Graafian) Follicle

A large fluid-filled secondary follicle ready for ovulation, characterized by a prominent fluid-filled antrum, zona pellucida, and surrounding corona radiata.

Corpus Luteum

The endocrine structure formed from the remnants of a ruptured mature follicle after ovulation that secretes progesterone, estrogens, relaxin, and inhibin.

Oogenesis

The formation and development of female gametes (oocytes) in the ovaries involving mitosis of oogonia into primary oocytes, followed by meiotic divisions producing a secondary oocyte and polar bodies.

Peg Cells

Nonciliated epithelial cells in the mucosal lining of the uterine tubes with microvilli that secrete a fluid providing nourishment to the ovum or zygote.

Stratum Functionalis

The superficial layer of the uterine endometrium that lines the uterine cavity and sloughs off during menstruation.

Stratum Basalis

The permanent deep layer of the uterine endometrium that gives rise to a new stratum functionalis after each menstruation.

Relaxin

A hormone produced by the corpus luteum and placenta that inhibits uterine smooth muscle contractions and increases pubic symphysis flexibility during labor.

LH Surge

A sharp spike in Luteinizing Hormone (LH) secretion triggered by high estrogen levels from an almost mature follicle via positive feedback, which brings about ovulation.