Lymphatic System
Nutrition-filled lymph drains from blood into the body tissues, into lymphatic tissues, then into the lymphatic system where it is filtered and returned to the bloodstream. It also plays a major role in the immune system, filtering out disease-causing organisms, producing specialized white blood cells and antibodies. Although joined to the cardiovascular system by a capillary system, the lymphatic system does not have a pump like the heart; this system relies on movement of the body to circulate fully.
Parts Involved
- Bone marrow – produces lymphocytes, B-lymphocytes mature here
- Thymus – T-lymphocytes mature here
- Lymph nodes – filtering, diagnosis and treatment glands (100+)
- Lymph vessels – everywhere that blood vessels exist, but off the pump
- Spleen – (accessory lymphatic organ)
- Tonsils – (accessory lymphatic organ)
- Appendix – (accessory lymphatic organ)
Functions
- Carries nutrition, water and oxygen to individual tissue cells
- Carries out tissue cell waste and enters it into the nodes and organs for filtering
- Filters lymph for foreign and unusable particles
- Houses various immune cells that clean, diagnose and attack
- Absorbs fats from the intestines
Fun Facts
Lymph nodes are most plentiful in the neck, armpits and the groin.
Chemicals in the eyes, stomach and mouth fluids fight infections.
Back to anatomical systems list
Muscular System
Muscles are responsible for every movement and all traveling that occurs within, all managed through coordination and pulling. There are about 700 muscles in the human body, about 600 of which are skeletal.
Parts Involved
- Skeletal muscles – muscles attached to skeleton that enable movement (come in pairs, usually contract voluntarily, and can twitch or sustain tension)
- Cardiac muscles – specialized striated muscles that comprise the heart (features include endurance and consistency)
- Smooth muscles – in the digestive system, blood vessels, bladder, airways and the uterus (can stretch, sustain tension and contract involuntarily)
- Tendons – tough, white, resilient extremities of muscles which connect to bone
- Fascia – fibrous membrane covering, supporting and separating muscles
Functions
- Contracting
- Relaxing
- Locking in place, preventing either motion
Fun Facts
Muscles are efficient at turning fuel into motion, they are long-lasting, they are self-healing and they are able to grow stronger with practice.
Lactic acid is produced when too little oxygen reaches the muscle.
Eyes are the busiest muscles in the body with movements estimated at 100,000 per day.
Back to anatomical systems list
Nervous System
Made up of your brain, your spinal chord, and a 47 mile network of nerves that thread through your body, the nervous system is the communication center for coordinating actions and reactions. Using chemistry, electricity and bundles of sensory cells (neurons), messages are rapidly delivered to and from your central nervous system.
When a nerve is stimulated, an electrical impulse is created, and travels down the finger of the neuron. At the end of the neuron, the impulse triggers chemicals to assist the impulse in jumping to the next neuron. This process repeats until the message is delivered, and occurs far faster than it took you to read this. Neurons can be very tiny, three feet long, and everything in between.
The somatic nervous system processes voluntary motor actions and the autonomic nervous system controls the actions that we do not willfully control. The autonomic nervous system is divided into the sympathetic and the parasympathetic subsystems, which work in tandem like our government’s branches of checks and balances (sometimes there’s a team and sometimes it’s gridlock). To learn more about the autonomic subsystems, peruse Neurology.
Parts Involved
- Brain & spinal chord – central nervous system
- Nerve pathways throughout the body make the peripheral nervous system
- Neurons – thin threads of nerve cells bundled together to form ‘telephone wires’ of communication
Functions
- Collects vast quantities of information about body state in relation to environmental state, analyzes and adjusts to satisfy needs, most powerfully, survival
- Controls body temperature, blood pressure, heart rate, breathing, physical motion et cetera
- Provides the means to think, dream, reason, experience and accomplish
Fun Facts
While some endocrine responses take hours, nerve impulses travel as fast as 250 miles per hour!
The human body has 47 miles of nerve pathways.
Back to anatomical systems list
Reproductive System
The reproductive system perpetuates our species by fusing two cells from different genders introduced through sexual intercourse or artificial insemination. Both genders create, ripen, store and transfer their respective sex cells (called gametes). Gametes in both sexes are created in a process called meiosis.
When gametes combine successfully, the merged sperm and ovum form a zygote; 7-10 days later, the still dividing and growing formation implants in the uterus and becomes an embryo. About eight weeks later, the embryo has developed into a fetus, which continues to develop into an infant, born after nine months of gestation.
Male Parts Involved
- Testes (contain seminiferous tubules) – where sperm are produced
- Scrotum – external bag of skin and muscles containing the testicles
- Epididymis – where sperm mature
- Vas deferens (ampulla) – narrow tube (about 18 inches long) connecting the epididymis to the ejaculatory ducts
- Seminal vesicle – creates and secretes nutrient-rich seminal fluid, filled with fructose and amino acids (sperm food) and vitamin C to combat the acidity of the female’s sexual tract
- Ejaculatory ducts – connect the vas deferens to the urethra
- Prostate – produces a milky secretion
- Cowper’s gland – produces a tiny amount of fluid in the outer penis that neutralizes any traces of acidic urine and lubricates the penis and female tract just prior to ejaculation (correlated to the female’s Bartholin glands)
- Penis (glans penis, prepuce, shaft and urethra) – places sperm inside the female
- Hypothalamus – secretes a hormone that contributes to sex organ function
- Pituitary gland – produces hormones that manage the sex organ function in both sexes, as well as some aspects of pregnancy and childbirth
- Adrenal cortex (zona reticulosa) – produces some testosterone is both sexes
Female Parts Involved
- Ovaries (oocytes, ovarian follicles) - stores immature eggs (oocytes) produced since birth
- Ovarian follicles (monthly fibro-vascular coatings produced around oocyctes) – produced around all oocytes that go through meiosis in monthly cycle, one of which secretes estrogen which triggers the thickening of the uterine lining and ripens the egg (ovulation)
- Fallopian tubes (fimbriae) – the fimbriae coax the ripened egg down the tube, where it is fertilized or not
- Uterus (cervix) – major female reproductive organ, connected to Fallopian tubes and the vagina via the cervix
- Vagina (4 inch elastic muscular tube) – receives sperm from male, serves as the birth canal and the means to release menstrual fluids
- Paraurethral glands (G-spot) – producing milky fluid similar to the male prostate , as many as 30+ surround the urethra and vicinity
- Vulva (mons pubis, labia majora and minora, prepuce, clitoral glans, clitoris and vagina opening) – external organs
- Bartholin glands – produce a lubricating substance in the outer vagina when she is sexually aroused (correlated to the male’s Cowper’s glands)
- Hypothalamus – secretes a hormone that contributes to sex organ function
- Anterior pituitary gland – produces hormones that manage the sex organ function in both sexes
- Adrenal cortex (zona reticulosa) – produces some testosterone is both sexes
- Corpus luteum – produces progesterone in both sexes
Fun Facts
According to the Guinness Book of World's Records, in the 18th century, a Russian peasant gave birth to 69 children over 40 years. Amongst them were 16 pairs of twins, 7 sets of triplets and 4 sets of quadruplets.
If an egg is not fertilized within 12-24 hours of being released from the follicle, it dissolves.
The clitoris is the only organ in humans seemingly designed purely for pleasure. It has twice the nerve endings of the entire penis.
Infant girls are born with 30,000 oocytes present in their ovaries! After reaching puberty, males typically produce 12 billion sperm per month!
Learn about research on how the male ‘pill’ may work.
