REPRODUCTIVE SYSTEM

The reproductive system or genital system is a system of sex organs within an organism which work together for the purpose of sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system.^[1] Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater geneticfitness of the offspring

The purpose of the organs of the male reproductive system is to perform the following functions:

• To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen)
• To discharge sperm within the female reproductive tract during sex
• To produce and secrete male sex hormones responsible for maintaining the male reproductive system

Unlike the female reproductive system, most of the male reproductive system is located outside of the body. These external structures include the penis, scrotum, and testicles.

• Penis: This is the male organ used in sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped part at the end of the penis. The glans, also called the head of the penis, is covered with a loose layer of skin called foreskin. This skin is sometimes removed in a procedure called circumcision. The opening of the urethra, the tube that transports semen and urine, is at the tip of the penis. The glans of the penis also contains a number of sensitive nerve endings.
  The body of the penis is cylindrical in shape and consists of three circular shaped chambers. These chambers are made up of special, sponge-like tissue. This tissue contains thousands of large spaces that fill with blood when the man is sexually aroused. As the penis fills with blood, it becomes rigid and erect, which allows for penetration during sexual intercourse. The skin of the penis is loose and elastic to accommodate changes in penis size during an erection.
  Semen, which contains sperm (reproductive cells), is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm). When the penis is erect, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.

• Scrotum: This is the loose pouch-like sac of skin that hangs behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum acts as a "climate control system" for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth or farther away from the body to cool the temperature.

• Testicles (testes): These are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubes are responsible for producing sperm cells.

The female reproductive system is designed to carry out several functions.

•  It produces the female egg cells necessary for reproduction, called the ova or oocytes.
•  The system is designed to transport the ova to the site of fertilization. 
• Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes.
•  The next step for the fertilized egg is to implant into the walls of the uterus, beginning the initial stages of pregnancy. 
• If fertilization and/or implantation does not take place, the system is designed to menstruate. In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.

What Parts Make up the Female Anatomy?

The female reproductive anatomy includes parts inside and outside the body.

The function of the external female reproductive structures (the genitals) is twofold: To enable sperm to enter the body and to protect the internal genital organs from infectious organisms. The main external structures of the female reproductive system include:

• Labia majora: The labia majora enclose and protect the other external reproductive organs. Literally translated as "large lips," the labia majora are relatively large and fleshy, and are comparable to the scrotum in males. The labia majora contain sweat and oil-secreting glands. After puberty, the labia majora are covered with hair.
• Labia minora: Literally translated as "small lips," the labia minora can be very small or up to 2 inches wide. They lie just inside the labia majora, and surround the openings to the vagina (the canal that joins the lower part of the uterus to the outside of the body) and urethra (the tube that carries urine from the bladder to the outside of the body).
• Bartholin's glands: These glands are located beside the vaginal opening and produce a fluid (mucus) secretion.
• Clitoris: The two labia minora meet at the clitoris, a small, sensitive protrusion that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.

SIGHT

The sense of sight serves to capture the light stimuli that affect the interior of our eyeballs, where photoreceptor cells are found. These stimuli are interpreted in the visual area of the brain to form the image we see through the eyes.

CorneaThis is the see-through skin that covers the front of your eye. It is clear like glass and it has no blood vessels in it.

ScleraThis is the tough skin which covers the outside of the eyeball. We call it the 'white' of the eye.

IrisThe iris controls the amount of light that enters the eye. The iris is the coloured part of your eye.

Pupil This is the hole in the coloured iris. It lets light into your eye.  It gets very small in bright light, and bigger in dull light.

The lensThe lens focuses light onto the retina. It changes shape to make sure that the 'picture' on the retina is as clear as possible.

Retina This is like a movie screen which shows the picture you are seeing - upside down, remember? The retina has two lots of cells called 'rods' and 'cones' Rods can 'see' black and white.  Cones can 'see' colours. They turn the picture into an electrical message for the brain. 

Optic nerve The electrical messages from the retina travel along the optic nerve to your brain. It's a bit like the cable that carries all the TV pictures from your aerial to your TV so that you can see the programs. The great thing is that our eyes take these 'movies' all the time and we don't need any film or camera.

Vitreous humour 
This is a thicker jelly-like liquid which fills the larger part of the eyeball and keeps it in shape. 

Choroid

Is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera.

Ciliary musclesThese are a circle of tiny muscles around the lens. They change the shape of the lens by squeezing and relaxing. They squeeze to look at nearby objects, and relax for far away objects.

BIBLIOGRAPHY

• http://www.cyh.com/HealthTopics/HealthTopicDetailsKids.aspx?p=335&np=152&id=1730
• http://tulandar5.wixsite.com/florihospital/2nd-floor-interaction
• http://kidshealth.org/en/kids/eyes.html
• http://www.biology-online.org/dictionary/Sight

OTHER GLANDS

Pituitary

Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system.It makes hormones that control several other endocrine glands.

The production and secretion of pituitary hormones can be influenced by factors such as emotions and changes in the seasons.

The tiny pituitary is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. The anterior lobe produces hormones such as:

• growth hormone
• prolactin, which activates milk production in women who are breastfeeding
• thyrotropin, which stimulates the thyroid gland to produce thyroid hormones
• corticotropin, which stimulates the adrenal gland to produce certain hormones

The posterior lobe of the pituitary releases antidiuretic hormone, which helps control the balance of water in the body. The posterior lobe also produces oxytocin, which triggers the contractions of the uterus in a woman having a baby.

Adrenal Glands

The body also has two triangular adrenal glands, one on top of each kidney.

The adrenal glands have two parts, each of which produces a set of hormones and has a different function:

1. The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.
2. The inner part, the adrenal medulla, produces catecholamines , such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress.

Pineal

The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin ,a hormone that may help regulate when you sleep at night and when you wake in the morning.

Reproductive Glands

The gonads are the main source of sex hormones. Most people don't realize it, but both guys and girls have gonads.

In guys the male gonads, or testes, are located in the scrotum. They secrete hormones called androgens, the most important of which is testosterone .

These hormones tell a guy's body when it's time to make the changes associated with puberty, like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy's body when it's time to produce sperm in the testes.

A girl's gonads, the ovaries , are located in her pelvis. They produce eggs and secrete the female hormones estrogen and progesterone. 

Estrogen is involved when a girl begins to go through puberty. During puberty, a girl will experience breast growth, will begin to accumulate body fat around the hips and thighs, and will have a growth spurt. Estrogen and progesterone are also involved in the regulation of a girl's menstrual cycle. These hormones also play a role in pregnancy.

Pancreas

The pancreas is also part of the body's hormone-secreting system, even though it is also associated with the digestive system because it produces and secretes digestive enzymes.

The pancreas produces two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.

THYROID GLAND

The thyroid’s main role in the endocrine system is to regulate your metabolism, which is your body’s ability to break down food and convert it to energy. Food essentially fuels our bodies, and our bodies each “burn” that fuel at different rates. This is why you often hear about some people having “fast” metabolism and others having “slow” metabolism.

The thyroid keeps your metabolism under control through the action of thyroid hormone, which it makes by extracting iodine from the blood and incorporating it into thyroid hormones. Thyroid cells are unique in that they are highly specialized to absorb and use iodine. Every other cell depends on the thyroid to manage its metabolism.

Derived from the Greek word meaning shield, the thyroid is a butterfly-shaped gland located in front of the windpipe (called the trachea) and just below the larynx or Adam’s apple in the neck. It is comprised of two halves, known as lobes, which are attached by a band of thyroid tissue called the isthmus.

During development, the thyroid is actually located in the back of the tongue and has to migrate to the front of the neck before birth.

HORMONES

The two main hormones the thyroid produces and releases are triiodothyronine and thyroxine.The thyroid also produces calcitonin, which helps control blood calcium levels.

The thyroid's hormones regulate vital body functions, including:

• Breathing
• Heart rate
• Central and peripheral nervous systems
• Body weight
• Muscle strength
• Menstrual cycles
• Body temperature
• Cholesterol levels

MOST COMMON ILLENS

Hypothyroidism , by contrast, stems from an underproduction of thyroid hormones. Since your body's energy production requires certain amounts of thyroid hormones, a drop in hormone production leads to lower energy levels. Causes of hypothyroidism include:

• Hashimoto's thyroiditis : In this autoimmune disorder, the body attacks thyroid tissue. The tissue eventually dies and stops producing hormones.
• Removal of the thyroid gland
• Exposure to excessive amounts of iodide
• Lithium

Untreated for long periods of time, hypothyroidism can bring on a myxedema coma, a rare but potentially fatal condition that requires immediate hormone treatment.

hyperthyroidism is due to an overproduction of thyroid hormones, but the condition can occur in several ways:

• Graves' disease: The production of too much thyroid hormone.
• Toxic adenomas
• Subacute thyroiditis: Inflammation of the thyroid 
• Pituitary gland malfunctions or cancerous growths in the thyroid gland

BIBLIOGAPHY:

• kidshealth.org
• endocrinesystem/wikipedia
• www.endocrineweb.com
• www.btf-thyrod.org
• www.innerbody.com
• www.webmd.com
• docs.wixstatic.com

ENDOCRINE SYSTEM

In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly. 

The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Many different hormones move through the bloodstream, but each type of hormone is designed to affect only certain cells.

WHAT IS A GLAND?

A gland is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere in the body.

Some types of glands release their secretions in specific areas. For instance, exocrine  glands, such as the sweat and salivary glands, release secretions in the skin or inside the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.

The major glands that make up the human endocrine system include the:

• hypothalamus
• pituitary gland
• thyroid
• parathyroids
• adrenal glands
• pineal body
• reproductive glands (which include the ovaries and testes)
• pancreas

PRÁCTICAS LABORATORIO:CEREBRO

1¿Cuántas meninges existen?¿Qué papel desempeñan?

Hay tres tipos,dura madre,aracnoides y pia madre que cubren todo el sistema nervioso central, añadiéndole una protección blanda que complementa a la dura de las estructuras óseas.

2¿Por qué nuestro cerebro tiene rugosidades?¿Cómo se llaman?

Las “arrugas del cerebro” 

están formadas por dos tipos de estructuras. Surcos, que corresponde a las hendiduras y giros, aquellas zonas en que las arrugas se muestran elevadas.

La zona arrugada del cerebro es la corteza cerebral, aquella que está más arriba y constituye la capa exterior. Se cree que parte de las arrugas se crean por un crecimiento rápido y diferenciado de la corteza cerebral, en que la materia gris crece más rápido que la blanca, formando así los pliegues para no verse limitada.

3¿Podrías indicar si existe alguna diferencia entre la disposición de la sustancia blanca en el cerebro y el cereblo con respecto a la médula espinal?

La sustancia blanca está compuesta de fibras nerviosas mielinizadas, las cuales contienen sobre todo muchos axones, Esta modula la distribución de los potenciales de acción, actuando como un retransmisor y coordinando la comunicación entre las diferentes regiones del cerebro.

La sustancia gris está compuesta por las somas y cuerpos neuronales, que no poseen mielina, y se la relaciona más con el procesamiento de la información.