Excretory System and Reproductive System

Excretory System

• Introduction:
  • Harmful materials are produced as a result of food metabolism in unicellular and multicellular organisms.
  • These harmful materials are called wastes, which must be discharged to avoid toxicosis and obstruction of biological functions.
  • Excretion is the removal of wastes produced in metabolic reactions.
  • Excretion maintains balance between cells and the environment and regulates water and salt balance.
• Types of Excretion in Humans:
  • Digestive excretion: Removal of faeces (undigested food materials, water, bacteria, and dead cells) via the digestive tract.
  • Pulmonary excretion: Removal of carbon dioxide and water vapour by the respiratory system.
  • Renal excretion: Filtration of blood to remove excess water and harmful materials like urea, which are then excreted via the urinary system.
  • Skin excretion: Removal of excess water, salts, urea, and a small amount of CO_2 through the skin.

Urinary System

• Structure of Urinary System:

  • Renal excretion is carried out by the urinary system, which consists of:

    1. Kidneys:
       • Two kidneys located on the back wall of the abdominal cavity, one on each side of the vertebral column.
       • Bean-shaped with the concave side towards the vertebral column.
       • Surrounded by a thin membrane called the capsule.
       • Composed of two main layers: cortex and medulla.
         • Cortex: Outer, red-colored layer containing microscopic filtering units called nephrons.
         • Medulla: Inner, bright-colored layer with a striped appearance due to urinary tubules; contains a central cavity called the pelvis, which is the beginning of the ureter.
       • Renal arteries nourish the kidneys, and renal veins remove wastes.
    2. Ureters:
       • Muscular tubes connecting the kidneys to the bladder, transporting urine.
       • Each ureter is approximately 22 cm long and consists of smooth muscles.
    3. Urinary Bladder:
       • A sac that stores urine, consisting of smooth (involuntary) muscles.
       • At the connection point with the urethra, there are circular striated (voluntary) muscles.

• Some Diseases of the Urinary System:

  • Diabetes Mellitus:
    • Caused by a decrease in the secretion of insulin hormone from the pancreas, leading to increased glucose levels in the blood.
    • High glucose levels damage organs, especially the eyes, skin, and kidneys.
    • Excess glucose is discharged in urine to balance blood glucose levels.
    • Symptoms: Quick fatigue, weight loss, thirst, and frequent urination.
    • Treatment: Insulin injections or tablets to reduce blood sugar levels, along with a diet low in starch and sugar.
    • Drinking sugary soda increases the chance of diabetes by over 20%.
  • Albuminuria:
    • Protein particles, like albumin, are filtered and discharged in urine due to kidney inflammation or disease.
    • Symptoms: Anemia, pale face, yellowish urine with hyper urination, burning during urination, and red spots on legs.
    • Remedies: Reduce protein and salt intake and drink more water.
  • Kidney Stones:
    • Increased dissolved salts in the blood, due to physiological, nutritional, or pathological disorders, leading to salt precipitation in the kidney pelvis, ureters, or bladder.
    • Common salts precipitated are phosphate and oxalate.
    • Symptoms: Frequent urination, severe pain in the lumbar region or body sides, bloody urination due to injuries in the urinary tract, and renal colic due to stone movement.
    • Remedies: Reduce intake of foods containing phosphate and oxalate (e.g., tomato) and consult a specialist physician immediately.

Skin Excretion

• Skin and its Importance:

  • The skin covers the body and protects it from external effects; it also discharges waste materials.
  • Human skin contains sweat glands, which play an important role in the discharging process.
  • Sweat glands remove excess water, salts, urea, and a little carbon dioxide.
  • The importance of sweat glands is evident during hot weather or hard muscular work when the body loses a significant amount of water and salts.

• Structure of Skin:

  • The human skin consists of two main layers: epidermis and dermis.

    1. Epidermis:
       • Composed of two layers: the outer keratin layer and the inner germinative (Malpighian) layer.
       • Keratin layer: The outermost layer, contains no blood vessels or nerve branches, composed of dead cells.
         • Dead cells are gradually removed during washing or itching and replaced by new keratinized cells from the germinative layer.
       • Germinative layer: Located under the keratin layer, consists of living cells that divide and produce new cells; contains nerve fiber ends and sweat gland ducts but no blood vessels.
         • Receives nutrients from blood plasma filtered from the dermis layer.
         • The color of the skin depends on pigment materials in the germinative layer, which increase upon exposure to sunlight.
    2. Dermis:
       • Consists of living tissues, including connective tissue, blood vessels, and nerves.
       • Connective tissue provides elasticity and strength to the skin.
       • The surface of the dermis layer is wavy, forming dermal papillae that contain blood vessels and nerve ends, representing the sense of touch.

• Skin Accessories:

  1. Hair:
     • Thin keratinized threads originated from the epidermis layer.
     • Each hair consists of a hair shaft, hair follicle, hair root, and sebaceous glands.
     • Sebaceous glands secrete a fatty liquid that keeps the skin from cracking and drying.
     • Each follicle is connected to smooth muscle fibers, the contraction of which erects the hair and elevates the skin around the hair.
  2. Nails:
     • Hard structures composed of hard, horn-like, keratinized dead cells, originated from the epidermis.
     • A nail has a root embedded in the dermis.
     • Nails protect the fingers and toe tips.
     • Regular cutting of nails is necessary, ensuring they are not excessively long.
  3. Skin Glands:
     • a. Sebaceous Glands:
       • Associated with hair follicles, secreting fatty liquids to keep skin from cracking and drying.
     • b. Mammary Glands:
       • Secrete milk containing nutrients for infants; nutrients are extracted from the mother's blood.
       • Nursing infants reduces the probability of blood cancer in mothers.
     • c. Sweat Glands:
       • Thin tubes coiled at the base, located in the dermis layer, surrounded by blood capillaries.
       • Ducts pass through skin layers and open to the surface through minute depressions called pores.
       • Human skin contains approximately two to three million sweat glands distributed throughout the body.

• Sweating:

  • Sweat contains 99% water and 1% solid materials, such as sodium salts, small amounts of urea, fatty acids, and amino acids.
  • Sweating supports the excretion process by discharging waste materials.
  • Environmental temperature is a primary factor affecting sweating.
  • Psychological conditions like fear (cold sweating) and muscular activity (exercise) increase sweating.
  • Sweating decreases during rest or quiet work.
  • Sweating is considered an important symptom in some diseases, such as fever or anemia.

Health of Skin

• Skin is very important for body health.
• Care guidelines:
  • 1. Have a bath periodically.
  • 2. Keep skin away from strong sunlight.
  • 3. Do not press on adolescent acne, as they are a natural result of some hormones.
  • 4. Do not get tattoos on your skin because they can cause allergic skin reactions.
  • 5. The clothes must not be too tight, because it limits muscle movement and blood circulation.
  • 6. We must visit the physician for skin diseases or abnormal symptoms on the body for its diagnosis and treating it before it spreads.
  • 7. The internal clothes which contact the skin must not be rough and harsh such as woollen clothes which irritate the skin and cause the scratching.

Reproductive System

• Introduction:
  • Reproduction is the production of new individuals (offspring).
  • The main purpose of reproduction is to continue the existence of living things.
  • Different reproduction methods exist in living things, all increasing the number of living things and transferring characteristics from one generation to another.
  • Human beings have reproductive organs that differ between males and females.

Male Reproductive System

• Consists of:

  • Glands that produce sperms.
  • Ducts through which sperms pass.
  • Additional organs that facilitate sperm transmission.
  1. Testes:
     • Two oval-shaped glands that produce male reproductive cells (sperms) and hormones responsible for secondary sexual characteristics in males (e.g., beard and moustache).
     • After formation, sperms pass through long coiled tubules into the vas deferens.
  2. Vas-deferens Ducts:
     • A pair of canals that transport sperms from the testis (or epididymis) to the urethra.
     • Epididymis is a long, coiled tube at the beginning of each vas-deferens duct, where sperms are stored until maturation.
     • Each vas-deferens duct opens into the urethra at the neck of the bladder.
     • Urethra opens to the outside via the male sexual organ.
  3. Seminal Vesicles:
     • Two sacs at the end of each vas-deferens duct near the neck of the bladder.
     • Store sperms after maturation.
  4. Associated Glands:
     • Secrete different liquids to protect, maintain, and facilitate the movement of male reproductive cells.
     • Include the prostate gland and Cowper's glands.

• Sperm:

  • Male reaches puberty around age 15.
  • Each sperm consists of a head, short neck, and long tail (for movement).
  • Each testis produces millions of reproductive cells during its activity period.

Female Reproductive System

• Composed of sexual glands that produce female reproductive cells (eggs) and ducts that transport these cells.
• Adapted to store fertilized eggs for development and nutrition of the fetus until birth.
• Consists of:
  1. Ovaries:
     • Two oval-shaped glands located at the lower part of the abdominal cavity on either side of the uterus.
     • Produce eggs and hormones responsible for secondary sexual characteristics in females.
  2. Oviducts (Fallopian tubes):
     • Tubes that transport eggs from the ovary to the uterus.
     • The beginning of the oviduct is funnel-shaped and partially covers the ovary.
  3. Uterus:
     • A large, pear-shaped organ with thick muscular walls.
     • The inner uterine cavity connects with the oviducts at the upper part.
• Ova Production:
  • Females reach puberty between ages 12-14, when the ovaries begin to produce ova.
  • A female produces no more than 400 mature ova during her lifetime.
  • Starting from puberty, females produce one ovum each month until ages 45-50.
• Menstruation:
  • If the ovum is not fertilized, it is discharged with blood, mucus, and some tissues in a process called menstruation.
  • Lasts from 4 to 7 days and happens approximately every 28 days.
  • Menstruation stops during pregnancy and after ages 45-50.

Secondary Sexual Characteristics

• Genital glands in males and females secrete hormones responsible for secondary sexual characteristics.
• Abnormalities in hormone secretion can affect the appearance of these characteristics.
• Differences between sexes:
  1. Hair density is greater in males.
  2. Breast growth and milk secretion occur in females but are inactive in males.
  3. The voice of males is sharper than that of females.

Fertilization and Pregnancy

• Fertilization:
  • Union of sperm nucleus and ovum nucleus to form a fertilized ovum (zygote).
  • Normally, a sperm unites with an ovum in the oviduct.
• Pregnancy:
  • The fertilized ovum passes into the uterus and attaches to the inner membrane.
  • It starts to divide and forms a fetus.
• Placenta:
  • An organ between the embryo and uterus that provides oxygen and nutrients to the embryo from the mother's blood and transports harmful materials to the mother's blood.
• Umbilical Cord:
  • Connects the embryo with the placenta.
  • Cut just after birth.
• Birth:
  • Pregnancy lasts about nine months.
  • The embryo develops in the uterus, and once maturation is completed, it leaves the mother's body through the birth process.
  • Milk starts to be secreted from the mammary glands just after birth.
  • Nursing protects the mother from disorders like breast cancer and supports the infant's immunity system.
• Caesarean Delivery:
  • In some cases, the birth process does not happen naturally, and the embryo is separated from the mother by caesarean delivery.
• Premature Birth:
  • Occurs when birth happens before nine months, around the 7th month.

Twins

• Normally, women give birth to one baby, but sometimes two babies can develop at the same time.

  1. Identical Twins:
     • Develop from the same fertilized egg, which divides into two independent cells after fertilization.
     • Have the same sex (male or female) and generally the same somatic characteristics (look alike).
  2. Non-identical Twins:
     • Develop when two or more ova mature at the same time and are fertilized separately.
     • Can have different or the same sex and different somatic characteristics.

Some Diseases of the Reproductive System

• Sterility:
  • The inability to produce sperm or ova in men or women.
  • Causes include hormonal deficiency, genetical diseases, or disorders of reproductive organs.
• In Vitro Fertilization (Artificial Fertilization):
  • Performed when there is any disorder in the male or female reproductive system that prevents natural fertilization.
  • The embryo is transported to the female uterus after fertilization, and the mother is supported by drugs to maintain pregnancy.

Effects of Smoking, Drugs, and Alcohol on Pregnancy

• Smoking:
  • Causes a decrease in oxygen levels and raises the carbon monoxide level in both the mother's and embryo's blood, creating an unhealthy environment for the embryo.
  • Increases the risk of miscarriage and premature birth or embryo death.
  • The effect of smoking continues beyond the birth of the baby, causing infections in the trachea and asthma.
• Herbal Medicine:
  • Avoid taking herbal medicine without a doctor's consultation.
• Alcohol:
  • Affects the embryo, causing nervous disorders and body malformation, especially in the face, as well as behavioral disorders.