Endocrine System and Reproductive Biology Lecture Notes

Comprehensive flashcards covering endocrine functions, hormone classes, pituitary and adrenal gland zones, lactation, and reproductive biology including fertilization and embryology.

Endocrine glands

Ductless glands that secrete hormones directly into the blood stream.

Paracrine

A type of cellular communication where a cell releases a hormone that affects neighboring cells.

Autocrine

A type of cellular communication where a cell releases a hormone that binds to receptors on its own surface.

Peptides and Proteins

Hormones that are easily broken down by proteolytic enzymes in the blood; examples include TRH, ADH, ACTH, insulin, and growth hormone.

Glycoprotein

Long strands of amino acids covered in carbohydrates, such as LH, FSH, and EPO (Erythropoietin).

Steroids

Hormones derived from the precursor cholesterol, including estrogens, androgens, glucocorticoids, and mineralocorticoids.

Fatty Acids

Hormones derived from arachidonic acid, such as prostaglandins, leukotrienes, and thromboxane.

Amines

Hormones derived from single amino acids, including thyroid hormones, dopamine, and melatonin.

Negative Feedback

The mechanism that controls the level of most hormones, where increasing hormone levels create a response to further inhibit release.

Positive feedback

A rare mechanism where a hormone brings about a response that triggers the further release of that hormone.

Anterior pituitary

An endocrine gland derived from oral ectoderm that communicates with the hypothalamus through the HHP system.

Posterior pituitary

Gland derived from an outgrowth of hypothalamic neurons that serves as a storage site for neurohormones.

HHP system

The hypothalamic-hypophyseal portal system consisting of a capillary plexus and portal veins used for transport between the hypothalamus and anterior pituitary.

CRH

Corticotropin-releasing hormone, which stimulates ACTH secretion from the anterior pituitary.

GnRH

Gonadotropin-releasing hormone, which stimulates the release of LH and FSH.

GHRH

Growth hormone-releasing hormone, which stimulates growth hormone secretion.

GAIH

Growth hormone-inhibiting hormone, which inhibits growth hormone secretion.

PIH

Prolactin-inhibiting hormone, which inhibits the release of prolactin.

Oxytocin and ADH

Hormones synthesized by hypothalamic neurons and transported along the hypothalamic-hypophyseal tract to be stored in axon terminals in the posterior pituitary.

$T_4$ (Thyroxine)

A thyroid hormone with a higher affinity for plasma proteins and found in higher concentrations in the blood.

$T_3$ (Triiodothyronine)

The most biologically important amine hormone of the thyroid, with a higher affinity for target cells.

Hypothyroidism

A condition characterized by cold sensitivity, anemia, dry hair, and weight gain.

Hyperthyroidism

A condition characterized by fatigue, weight loss, hunger, and sensitivity to heat.

Chief cells

Cells within the parathyroid gland that produce PTH to control calcium and phosphate levels.

PTH (Parathyroid Hormone)

A hormone that stimulates the release of calcium and phosphate from bone and increases phosphate excretion by the kidney.

Zona glomerulosa

The zone of the adrenal cortex that secretes mineralocorticoids like aldosterone, which enhance water reabsorption and $K^+$ excretion.

Zona fasciculata

The zone of the adrenal cortex that secretes glucocorticoids (cortisol and corticosterone) during stress, regulated largely by ACTH.

Zona reticularis

The zone of the adrenal cortex that secretes androgens serving as precursors for sex steroids.

Catecholamines

Epinephrine and norepinephrine, produced in the adrenal medulla to facilitate the fight-or-flight response.

Prolactin

A peptide hormone released from the anterior pituitary that controls milk production.

Alveoli

The part of the mammary gland where milk is synthesized, surrounded by myoepithelial cells that respond to oxytocin.

Mastitis

An infection of the mammary gland.

Leydig cells

Cells in the testes that possess LH receptors and respond by secreting testosterone.

Sertoli cells

Cells in the testes that possess FSH receptors and synthesize ABP (androgen binding protein) and inhibin.

Blood-testis barrier

A barrier formed by tight junctions between Sertoli cells that prevents the immune system from attacking cells during spermatogenesis.

Capacitation

The further maturation of sperm and removal of semen proteins occurring in the female vagina.

Acrosomal process

The event where the sperm makes contact with the egg and its acrosome penetrates the zona pellucida.

Zygote

A diploid cell formed from the fusion of the sperm and ova nuclei in the oviduct.

Ectoderm

The primary germ layer that forms the epidermis, CNS, sense organs, and neural crest.

Endoderm

The primary germ layer that forms the lining of the digestive and respiratory tracts.

Mesoderm

The primary germ layer that forms the skeleton, muscle, heart, and gonads.

Morula

A solid ball of cells formed during the cleavage stage of the embryo.

Blastula

A hollow ball of cells formed during early embryonic development.

hCG (Human Chorionic Gonadotropin)

A pregnancy test hormone created by trophoblast tissue that rescues and maintains the corpus luteum.