BODY SYSTEMS
1.SENSE ORGANS • Stimuli: changes that occur in our internal and external environment. • Sensory receptors: specialised structures that detect stimuli and generate nerve impulses. • Depending on their location internal or external in the body can be: • Interoceptor: distributed throughout the inside of the body, detect changes such as variations in blood oxigen levels or blood pressure. • Exteroceptors: near the surface of the body, detect changes in the external environment ex. T or light.
1.1.THE EAR Outer ear • Auricle (1) cartilaginous structure covered in skin, directs sound to the ear canal. • Ear canal (2) contains small hairs and glands that secrete earwax (cerumen). Middle ear • Chain of ossicles (3) three tiny bones: malleus, incus and stapes • Eardrum (4) membrane that vibrates when sound waves reach it. • Eustachian tube (5) keeps equal pressure on both sides of the eardrum. Inner ear • Vestibular system (6), whith utricle and saccule are responsible for balance. • Cochlea (7), spiral tube that contains sensory cells that detect sound and transform into nerve impulses.
HEARING ▪ Sound waves reach the auricle and are transmitted through the ear canal to the eardrum, which vibrates. ▪ The eardrum transmits the sound waves to the chain of ossicles. ▪ The stapes sends the sound waves to the inner ear, causing the movement of the fluid (endolymph) in the cochlea, that stimulates the cells which are sensitive to vibrations. They generate nerve impulses that are sent to the brain via the auditory nerve.
Dynamic balance: walking, running, cycling, etc. • Controlled by the semicircular canals, which are full of endolymph. When we move, the endolymph moves. The sensory cells detect this movement and generate nerve impulses that are sent to the brain. • Static balance: keep our body in the same position when we are not moving. • The utricle and saccule detect if we are sitting down, standing up, lying face up(to), to lie on the back, etc.
1.2.THE EYE; EYEBALL The eyeball: Spherical structure located in a cavity in the skull called the orbit. Three layers: ▪ Retina (4), internal layer, contains photoreceptor cells: ▪ Cones (colors) ▪ Rods (black and white / night vision), ▪ The fovea is an area with high density of cones, responsible of sharp vision. ▪ Choroid (5), middle layer, contains many blood vessels that provide the eye cells with nutrients. ▪ Sclera (6), opaque, white outer layer: the front part (cornea) is transparent. ▪ Aqueous humour (1): transparent fluid between cornea and crystalline lens. ▪ Crystalline lens (2): elastic, transparent, biconvex structure behind the iris. ▪ Anatomical blind spot (3): optic nerve is connected in this area, no cones or rods. ▪ Vitreous humour (7): transparent, gelatinous fluid, fills chamber between crystalline lens and retina. ▪ Iris (8): circular structure. Colour varies from person to person. Pupil is the hole in it’s center. Diameter of pupil changes regulating the amount of light that enters.
SIGHT▪ Depending on where the eye focusses, pupil and crystalline lens are adapted. ▪ Pupil dilates or contracts. ▪ Crystalline lense undergoes accommodation, changes it’s thickness.
1.3.THE SKIN ▪ Largest organ in our body, responsable for most of our sense of touch. ▪ Consists of three layers: ▪ Epidermis: outer layer, epitelial tissue. Outermost cells are dead. ▪ Dermis: inner layer, connective tissue. Contains: ▪ Capillaries • Hair follicles • Sweat glands • Sensory receptors ▪ Hypodermis: deepest layer, mainly adipose cells, protective and thermoregulatory function. Sensory receptors in dermis layer Can be: • Free nerve endings (nociceptors): detects pain. • Groups that form corpuscles: ▪ (1) Krause’s corpuscle: detects cold. ▪ (2) Pacinian corpuscle: detects pressure and vibrations. ▪ (3) Meissner’s cospuscles: detects textures. ▪ (4) Merkel’s discs: detects pressure. ▪ (5) Ruffini corpuscle: detects heat.
1.4. THE NOSE ▪ The olfatory cells, which are located in the upper lining of the nasal cavity form the olfactory epithelium. ▪It contains glands that secrete the mucus. We can only smell substances if they are disolved in mucus and present in sufficient concentration. ▪When olfactory cells are stimulated, they send nerve impulses from the olfactory bulb through the olfactory nerve to the brain, which interprets the information and identifies the smell. 10 classes of smells ▪woody/resinous, Fragrant, Fruity (non-citrus), Chemical, Minty/peppermint, Sweet, Lemon, Popcorn, Pungent and decayed.
1.5. THE TONGUE✓ Responsible for our sense of taste.✓ Its surface is covered in taste buds to form papillae.✓ The taste buds contain chemoreceptors that detect substances in foods that are dissolved in saliva. They send nerve impulses through the gustatory nerve to the brain, which interprets and identifies tastes. ▪4 basic tastes: ▪ Sweet, salty, sour and bitter.
2.1. THE SKELETAL SYSTEM • Made up of BONES, to which muscles are attached, as well as cartilage. • BONES: Hard structures formed of collagen, a protein, as well as phosphorus and calcium salts. • An adult human has 206 bones. • Composed mainly of: ✓compact bone tissue on the outside and ✓spongy bone tissue at the core.THE SKELETAL SYSTEM • Together the bones form the skeleton, two sections: Axial skeleton made up of the skull, thorax and spinal column. Appendicular skeleton made up of the upper and lower limbs.: • Depending on their shape, there are three types of bones: 1. Long (ex. femur) 2. Short (ex. vertebrae, wrist, hand) 3. Flat (ex. skull, scapula)
The long bones are made up of • Cartilage, a cartilaginous tissue that surrounds the epiphysis at the joint. • Epiphysis, thick end of long bone, spongy bone tissue filled with red bone marrow (in which blood cells are produced). • Endosteum, layer of connective tissue lining internal cavity of diaphysis. • Diaphysis, long middle section, compact bone tissue filled with yellow bone marrow (made up of adipossse tissue) • Periosteum, layer of connective tissue that surrounds the bone.
Bones have several functions: P Provide a framework for the body. P Provide structures to which muscles are attached. P Protect organs, (such as brain and spinal cord). PContain red bone marrow, produces red blood cells. PStore calcium, which is released into the blood if required.
CARTILAGE is softer than bone and formed of cartilaginous tissue: •Nose •Ears •Intervertebral discs (between the vertebrae) Cartilage also forms the embryonic skeleton. Because cartilage is softer than bone, it is more flexible. Joints ▪ Structures that connect two bones. ▪ Three types 1. Immovable joints (in the skull). 2. Slightly movable joints (in spinal column). 3. Movable joints (knee, elbow, shoulder, etc.), consist of ◦ Ligaments, groups of fibres that connect the bones. ◦ Cartilage, covers the surface to prevent friction. ◦ Synovial cavity, space between the bones, filled with viscous fluid (lubricant)
2.2. THE MUSCULAR SYSTEM ▪ Made up of skeletal muscles. ▪ These muscles are formed of striated muscle tissue: ✓ contains long cells with several nuclei: muscle fibres. ▪ Human body contains 650 skeletal muscles approx. ▪ Maintain posture and generates movement. muscle (5), surrounded by epimysium (4), formed of – Muscle fascicle (1), surrounded by perimysium (2), formed of • Muscle fibres, surrounded by endomysium (3) • Tendon (6), strong structure of fibrous connective tissue. Connects muscle to bone and transmits muscle contraction.
TYPES OF MUSCLES: Fusiform muscles: They are long and spindle-shaped. They are involved in movement. Flat muscles They are square or fan-shaped. They cover organs. Circular muscles They are ring-shaped. They open or close ducts or cavities.
MUSCLE CONTRACTION The striated muscle tissue that forms muscles contracts quickly and voluntarily. To do this, it requires calcium, energy and oxygen. • Certain stimuli cause muscle fibres to shorten (contract). • The muscles lengthen (relax) when the stimuli stops.
• This generates movement. To extend the forearm, the triceps contracts and the biceps relaxes. To flex the forearm, the biceps contracts and the triceps relaxes.
DISEASES THAT AFFECT THE EARS •Otitis: inflammation of part of the ear ▪ Otitis externa, ear hurts when touched or pulled. ▪ Otitis media, fluid behind ear drum. ▪ Otitis interna, common symptom is vertigo. •Deafness: partial or total inability to hear. ▪ Hereditary. ▪ Malformations. ▪ Infections. ▪ Tumors. ▪ Traumatic injuries. ▪ Prolonged exposure to loud noises. Diseases that affect the eyes ▪ Conjunctivitis: inflammation of conjunctiva, caused by allergies, irritants or infections. ▪ Astigmatism: optical defect caused by irregular curvature of cornea or crystalline lense. Objects appear distorted. ▪ Long sight (hypermetropia): inability to focus on near objects. Images are formed behind retina, corrected with converging lenses. ▪ Short sight (myopia): inability to focus on distant objects. Images are formed in front of retina, corrected with diverging lenses.
DISEASES THAT AFFECT THE EYES▪ Presbyopia: loss of ability to accommodate in the crystalline lens. Causes por near vision, associated with ageing. ▪ Blindness: caused by problems in nervous system or eyes. ▪ Cataracts: Clouding of crystalline lens or vitreous humour, can eventually cause blindness. Associated with ageing and diabetes.▪ Glaucoma: caused by increasing pressure of intraocular fluid. Affects vision, can cause light sensitivity and even blindness. ▪ Colour blindness: hereditary disease caused by a lack of one type of cone.
DISEASES THAT AFFECT THE SKIN ▪ Dermatitis: inflammation of skin, caused by allergies, irritants or other diseases, treated with creams. ▪ Psoriasis: skin cell overproduction, they get replaced every few days instead of every month. Other symptoms: flaking, inflammation, heat, itchiness, pain and redness of the skin. Treated with medicines, creams and phototherapy.
DISEASES THAT AFFECT THE BONES ▪ Fissure: crack in a bone. ▪ Fracture: break in a bone, causes intense pain, bruising, swelling, limited mobility. Can be treated with plaster cast or splint, sometimes requires surgery. ▪ Osteoporosis: caused by loss of bone mass and deterioration of bone structure. P Bones fracture easily. P Treatment involves medicines, exercise and consuming enough calcium. ▪ Spinal defects✓ Scoliosis (sideways curvature) ✓Hyperlordosis (excessive curvature of lumbar spine) ✓ Kyphosis (excessive curvature of dorsal spine —> hump) Scoliosis Fractured bone.
DISEASES THAT AFFECT THE JOINTS ▪ Arthritis: inflammation of joint. ▪ Causes pain, inflammation, redness and joint deformities ▪ Osteoarthritis: breakdown of cartilage increases friction in joint. ▪ Treated with medicines, sometimes replacement of joint with prosthesis ▪ Gout: type of arthritis caused by uric acid crystals forming in joints. ▪ Sprain: overstreched or torn ligament. ▪ Symptoms are swelling, pain, bruising and limited mobility of the joint. ▪ Dislocation: end of a bone leaves it’s normal position in joint. ▪ Causes intense pain, inflammation and deformed joint, treated by relocating the bone.
DISEASES THAT AFFECT THE MUSCLE AND TENDONS ▪ Muscle contracture: painful, long-lasting, involuntary contraction. ▪ Treated with physiotherapy and applying heat ▪ Strained muscle: torn muscle fibres, caused by overstretching or impact. ▪ Tendonitis: inflammation of a tendon. ▪ Generally caused by overuse, bad posture or too much exercise. ▪ Treated with medicines, rest and physiotherapy.
NERVE CELLS Nervous tissue is made up of two types of cells: Neurons and neuroglia • Neurons • Highly specialised cells. • Star-shaped cells unable to divide. • Initiate and transmit nerve impulses. • Made up of • Soma (1) • Dendrites (2) • Axon (3) Neuroglia: Located between neurons, they support, nourish and protect them. • Astrocytes (1), nurture neurons, remove neurotransmitters • Oligodendrocytes (2), wrap around several axons, form an insulating layer called the myelin sheath. • Schwann cells (3), wrap around a part of
one axon, form an insulating layer called the myelin sheath.
NERVE IMPULSES AND SYNAPSES Excitation of a neuron generates a nerve impulse. This is an electric current passing along the neuron from dendrite to axon. It always travels in one direction: it enters through dendrites, travels to the soma and leaves through the axon. Nerve impulses can pass to other neurons through connections between axons and dendrites called Synapses. ▪ Presynaptic terminal: end of axon, contains synaptic vesicles that store the neurotransmitters. ▪ Synaptic cleft: small space between two neurons, they never touch. ▪ Postsynaptic terminal: Dendrite or soma of second neuron
THE NERVOUS SYSTEM Responsible for coordinating all functions of the body, intellectual function, emotions and feelings. Divided into central nervous system (CNS) and peripheral nervous system (PNS) CNS = Brain + spinal cord PNS = All the nerves + nerve ganglia throughout the body.
CENTRAL NERVOUS SYSTEM (CNS) u At microscope level: uwhite matter (neuron axons with myelin sheath) u and grey matter (soma and dendrites) uBrain is protected by the skull, spinal cord is protected by spinal column. uMeninges for further protection u Pia mater (inside) u Arachnoid mater (middle) : both Surrounded by cerebrospinal fluid for protection. uDura mater (outside)
THE BRAIN: Cerebrum, Cerebellum and Brain Stem 1. CEREBRUM Two hemispheres, separated by the great longitudinal fissure and connected by corpus callosum (white matter) Cerebral cortex: outer layer, rough full of folds and furrows, formed of grey matter, functions : Receiving, interpreting and processing from sense organs. Initiating voluntary motor responses. Intellectual and mental functions (intelligence, memory, language and communication, learning, awareness, choices, etc.)Limbic system: Contains pituitary gland regulates endocrine system. Responsible for emotions, feelings and basic instincts.
THE BRAIN: Cerebrum, Cerebellum and Brain Stem 2. CEREBELLUM Tightly folded grey matter with white matter on inside. Responsible for motor coordination and balance. 3. BRAIN STEM Connected to spinal cord. Formed of white matter on outside and grey matter on inside Regulates autonomic functions: Heartbeat Respiratory movements Blood pressure, etc.
THE SPINAL CORD Connected to brain stem. Extends down the back of the body, protected by spinal canal formed by vertebrae. White matter on outside, grey matter on inside Two functions Conduit function: takes information from sense organs to brain and response from brain to effector organs. Reflex function: initiates involuntary motor responses. The autonomic nervous system u Subdivided into u Sympathetic nervous system u Prepares body for emergency, react to stress, fear, etc…, increases energy expenditure. u Dilates pupils, increases heartbeat, inhibits activity of digestive system. u Parasympathetic nervous system u Associated with situations of rest and calm, decreases energy expenditure. u Activates digestive system, slows heartbeat
THE AUTONOMIC NERVOUS SYSTEM u Subdivided into uSympathetic nervous systemu Prepares body for emergency, react to stress, fear, etc…, increases energy expenditure. u Dilates pupils, increases heartbeat, inhibits activity of digestive system. uParasympathetic nervous systemuAssociated with situations of rest and calm, decreases energy expenditure. u Activates digestive system, slows heartbeat.
SOMATIC NERVOUS SYSTEM This part is formed of: Sensory nerves: connect the sense organs to the nerve centres. Motor nerves: connect the nerve centres to the skeletal muscles. ▪ It controls voluntary acts and reflexes.
VOLUNTARY ACTIONS AND REFLEXES Reflexes are generated unconsciously in spinal cord, involve system of three neurons (reflex arc). 1. A receptor which perceives the stimulus (ex. A pin prick) 2. A sensory neuron which transmits the impulse to the spinal cord. 3. An interneuron located in
the grey matter of the spinal cord generates an immediate response order. 4. A motor neuron along which the order travels to the effector organ 5. An effector organ (ex. A muscle) which executes the response (in this case it contracts and we pull our hand away). Voluntary actions are generated consciously in cerebral cortex 1. A receptor which perceives the stimulus. 2. A sensory neuron which transmits the impulse to the spinal cord and from there to the cerebral cortex. 3. The cerebral cortex turns the information into a conscious sensation (image, shape, feeling of cold, etc..) and uses both this and stored prior experiences to generate a response order which it then sends through the spinal cord to a motor neuron. 4. A motor neuron along which the order travels to the effector organ 5. An effector organ (ex. A muscle) which contracts voluntarly.
THE ENDOCRINE SYSTEM System for coordination and control of body functions. Made up of endocrine glands that manufacture and secrete hormones: Chemical messengers. Released directly into blood stream. Transported to their target organs. Nerve information They provide a quick response that lasts a short time. Endocrine information Their response is slower and lasts longer. Its function is regulated by nervous system through (hypothalamic-pituitary axis): u The hypothalamus send out releasing hormones which stimulate the secretion of pituitary hormones. u The pituitary hormones act on their target organs. u When enough of these final hormones are released, they act on the hypothalamus and pituitary gland, preventing the secretion of their respective hormones. This stop the cascade of hormone release.
THE MALE REPRODUCTIVE SYSTEM PENIS • Formed of erectile tissue, a connective tissue with large spaces that fill with blood when is erect. • The erectile tissue is found in the three regions that form penis: • Two corpora cavernosa • Corpus spongiosum • Corpus spongiosum surrounds urethra, keeping it open at all times. It widens at the end to form: • Glans: very sensitive area, protected by foreskin. TESTICLES • Two oval shaped organs inside a sack of skin (scrotum) and outside the abdominal cavity. • Each testicle is formed of
millions of seminiferous tubules. • Walls of seminiferous tubules contain the sperm precursor cells. • Temperature of testicles is about 3ºC lower than body temperature, this is essential for spermatogenesis. • There are other endocrine cells between seminiferous tubules which produce androgens (testosterone).
GENITAL TRACT Consists of ducts that take sperm to outside: • Epididymis: • Long, coiled tube attached to the top of each testicle. • Sperm is stored here while it matures. • Vas deferens: • Part of epididymis, passes through prostate and empties into urethra. • Secretions from accessory glands empty into vas deferens. • Urethra: • Duct shared by reproductive and excretory system. • Expells semen and urine from body. ACCESSORY GLANDS Secrete substances that mix with sperm to form semen: • Seminal vesicles: • Located behind urinary bladder. • Empty into final part of vas deferens. • Produce seminal fluid rich in fructose = energy for sperm. • Prostate gland: • Located underneath bladder, surrounding urethra. • Produces prostatic fluid. • Activates sperm and neutralises acidity of female mucous secretions. • Cowper’s glands; • Located at base of penis. • Secrete lubricating fluid that neutralises acidity of urethra.
THE FEMALE REPRODUCTIVE SYSTEM EXTERNAL GENITALIA • Called vulva, formed of: • Labia majora, two folds of skin that cover the • Labia minora, two thinner folds • Clitoris, a very sensitive organ near the top junction of the labia minora: it is the female equivalent of the male glans.
GENITAL TRACT Formed of the ducts that take the eggs to outside: • Fallopian tubes • Two ducts that empty into uterus. • Connected to ovaries by infundibulum. • Uterus • Hollow, muscular organ, shape of an upside-down pear. • Narrow section at bottom is cervix, connected to vagina. • Wall of uterus is formed of myometrium, thick layer of smooth muscle. • Inside is covered with endometrium, epitelial cells with many blood vessels. • Vagina • Elastic duct formed of walls of muscle. • Connects cervix to outside. • Glands on vaginal wall secrete lubricants. • External opening is partially covered by a membrane (hymen)
OVARIES • Size and shape of an almond. • Suspended in abdominal cavity by small ligaments. • Produce eggs and female hormones (oestrogens and progesterone). • Made up of medulla (inside part) and cortex (outside part). • Cortex contains numerous spherical cavities called follicles. • Follicles contain immature eggs (oocytes). • Oestrogens and progesterones are synthesised in follicles at different times during menstrual cycle. • When mature follicle releases egg it converts to a corpus luteum
FORMATION OF GAMETES
SPERMATOGENESIS ▪ Sperm formation takes place in the testicles. ▪ Process begins in puberty. ▪ Beginning of puberty is marked by first ejaculation. ▪ From that moment there is a continuous sperm production, decreases with testosterone levels at older age. ▪ Four phases of spermatogenesis • 1. Multiplication pase: Spermatogonia divide to form new spermatogonia • 2. Growth phase: spermatogonia increase in size and become spermatocytes • 3. Maturation phase: spermatocyte divides (meiosis) to form four spermatids • 4. Differentiation phase: spermatis transform to become sperm.
SPERM • Sperm consist of three parts: • Head: • Contains nucleus with 23 chromosomes. • A human has 46, so half of them come from the egg. • Contains acrosome, an organelle containing enzymes to dissolve outer layer of ovum. • Midpiece: • Contains numerous mitochondria. • Tail: • Moves thanks to energy provided by mitochondria.
OOGENESIS • Egg formation (oogenesis) occurs inside the ovarian follicles. • Process begins before birth and stops at oocyte stage. • Restarts in puberty. • Oocytes mature to become eggs in a cyclical process: the ovarian cycle. • The ovarian cycle occurs every 28 days approx. alternating between two ovaries. • Cycle starts with menarche (first period) during adolescence and continues until menopause.
OOGENESIS • Four phases of oogenesis: • 1. Multiplication phase: oogonia, cells in ovarian cortex divide and form new oogonia. • 2. Growth phase: oogonia grow increasing in size to become oocytes. • 3. Maturation phase: oocytes divide (meiosis) to form four cells, only one becomes an ootid, the other three are polar bodies that disappear. • 4. Differentiation phase: ootid undergoes small changes to become an egg.
THE OVARIAN AND MENSTRUAL CYCLES • They are regulated by pituitary gland and ovarian hormones. • They occur approximately every 28 days if no fertilisation has occurred. • The ovarian cycle: changes that occur in the ovary so that an egg can be produced, mature and be released. It also produces female sex hormones. It occurs during oogenesis, alternating between the two ovaries. • The menstrual cycle: changes that occur in the endometrium of the uterus to prepare it for implantation of the embryo. It occurs periodically.
THE OVARIAN CYCLE 1st Follicular phase: • Starts on the first day of a period and lasts about 14 days. • The pituitary gland produces FSH , which stimulates the ovaries, maturating of a follicle and the oocyte it contains. • As the follicle grows, it starts to produce oestrogens. 2nd Ovulation: • Occurs approximately on day 14, when the levels of FSH and oestrogens are at their highest. • The pituitary gland starts to release LH, causing the mature follicle to rupture and release an egg into the Fallopian tubes. • During and just after this period, the woman is fertile. 3rd Luteal phase: • Lasts approximately between day 15 and day 28. • If fertilisation has not taken place, on day 28 the woman starts her period. • The broken follicle transforms to become the corpus luteum. • LH stimulates the corpus luteum to secrete progesterone.
THE MENSTRUAL CYCLE 1st Proliferative phase: • Begins when menstruation ends and lasts until ovulation. • The oestrogens produced by the ovarian follicle stimulate the endometrium in the uterus, causing it to thicken.
2nd Secretory phase: • Starts after ovulation and continues until the start of the next period. • Progesterone secreted by the corpus luteum causes maximum thickening of the endometrium, preparing it for possible implantation of a fertilised ovum. 3rd Menstruation: • Starts on the first day of the cycle and lasts between five and seven days. • If fertilisation has not taken place during the previous cycle, the corpus luteum breaks down in the ovary and stops producing progesterone. This causes the endometrium to break away.