Endocrine System Chapter 15 Endocrine System Comprised of ductless glands that secrete hormones into the blood stream Hormones travel through circulation until they reach their target cell Results in a slow but a prolonged response Major glands of the endocrine system Anterior pituitary gland Controlled by hypothalamic releasing and hypothalamic inhibiting hormones Hormones produced by the anterior pituitary Thyroid stimulating hormone stimulates the thyroid to produce thyroid hormones Adrenocorticotropic hormone stimulates the adrenal cortex to produce cortisol Gonadotropic hormones stimulates gonads to produce sex cells and hormones Prolactin stimulates mammary glands to develop and produce milk only after child birth Growth hormone promotes skeletal and muscular growth Neurons in the gypothalamus have axons that extend down into the posterior pituitary the synaptic knobs of these neurons release hormones directly into circulation Antidiuretic hormone released in response to dehydration Decreases urine production Oxytocin stimulates uterine contractions during childbirth and promotes milk let down plays a role in ejaculation in males Posterior pituitary gland Thyroid gland A large gland located below the larynx Iodine is needed in the diet to allow the thyroid gland to produce the hormone The thyroid also secretes calcitonin helps lower blood levels by stimulating the deposition of calcium in the bones what if someone lacks iodine in their diet Parathyroid glands Small glands embedded in the surface of the thyroid gland Produced parathyroid hormone Acts to increase blood calcium levels by promoting osteoclast activity Promotes reabsorption of calcium by the kidneys Adrenal glands Located on the top of the kidneys 2 parts to each gland Adrenal medulla Inner portion of the adrenal glands Hypothalamus triggers production and secretion of hormones from the adrenal medulla Produces hormones that allow a short term response to stress Epinephrine Norepinephrineuter Adrenal cortex Outer portion of the adrenal glands Produces hormones that provide a long term response to stress Pancreas Testes Located behind the stomach Composed of 2 tissue Exocrine produces and secretes digestive juices Gonads found in males Produce androgens Stimulates growth of the penis and testes Responsible for secondary sex characteristics such as facial underarm and pubic hair prompts the larynx and vocal cords to enlarge promotes muscular strength Ovaries gonads found in females produce estrogen and progesterone stimulate growth of the vagina and uterus responsible for secondary sec characteristics such as females body hair responsible for egg maturation regulates the menstrual cycle Thymus gland Pineal gland lies beneath the sternum this gland is the largest and most active during childhood secretes hormones called thymosins that aid in differentiation of lymphocytes located in the brain secretes melatonin regulates the sleep wake cycle may also regulate sexual development The Pituitary Located beneath the hypothalamus which helps to regulate its functioning Divided into the anterior and posterior pituitary The two components operate in different ways What happens when the body produces too much or too little Gh Pituitary dwarfism too little Gh is produce during childhood results in small stature Giagantism too much GH is produce during childhood results in excessive growth Acromegaly overproduction of Gh is produced during childhood results in excessive growth Calcitonin 9 DNA in somatic and sex cells Somatic cells Reproductive system Chapter 16 Each somatic cell has 46 chromosomes 23 pairs within the nucleus Cells that have pairs of chromosomes are called diploid 2N Sex cells Gametes Gametes eggegg and and sperm sperm have have only only 2323 chromosomes chromosomes 11 of of each each pair pair in their nuclei Cells that have only 1 of each pair of chromosomes are called haploid N During fertilization a sperm and egg combine to form a zygote and the chromosome number is restored to the diploid number of 46 Mitosis and meiosis Mitosis Meiosis Is a type of cell division in which a cell makes an exact copy of itself This process is used for growth and repair of tissues Used by somatic cells cells other than germ line cells Is a type of cell division in which a cell halves the number of chromosomes This process is used to form eggs and sperm Used by germ line cells Reproductive System Sex Determination Males have an X and a Y chromosome The Y chromosome contains the SRY gene Encodes testes determining factor TDF Females have two X chromosomes Lack a SRY gene Default pathway Male Anatomy Scrotum and testes Scrotum Sac that holds the testes Helps to regulate the temperature of the testes Testes Paired organs that produce sperm and male sex hormones Composed of seminiferous tubules where sperm are produced Interstitial cells produce testosterone Testes Spermatogenesis Sperm are produced within the seminiferous tubules of the testes Ovaries and other female productive structures develop in absence of TDF Sertoli cells help nourish sperm and regulate the process of sperm production Sperm spermatozoa are stored and mature in the epididymis Sperm anatomy 3 parts the egg Head covered by a cap called the acrosome which stores enzymes needed to penetrate Middle piece contain mitochondria to make energy ATP Tail provides movement for the sperm Vas deferens and urethra Vas deferens Transports sperm to the urethra Urethra Transports sperm out of the body 3 glands that contribute to semen Can enlarge with age Penis Penis Contains erectile tissue Highly vascularized How does Viagra work Seminal vesicles produce a fructose containing fluid that provides energy for the sperm Prostate gland contributes 60 of fluid to semen Bulbourethral glands secretes an alkaline fluid and lubricants Viagra treats erectile dysfunction by inhibiting the enzyme that breaks down cGMP As long as cGMP remains available vaosdilation continues Hormonal regulation in males Gonadotropin releasing hormone GnRH secreted by the hypothalamus to control release of other hormones such as FSH and LH Follicle stimulating hormone FSH secreted by the anterior anterior pituitary pituitary promotes promotes the te production production of o sperm sperm Luteinizing hormone LH secreted by the anterior pituitary triggers the production of testosterone Testosterone important for normal development and functioning of the male reproductive organs Hormonal regulation in
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