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Showing posts from 2011
Muscle contraction
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Skeletal muscles contain muscle fibres which span the whole length of the muscle. These are made up of subunits called sacromeres containing thick myosin filaments and thin actin filaments. Thick and thin filaments slide towards each other during contraction, the total effect of multiple sacromeres contracting leads to the shortening of the muscle.
How resting membrane potentials are established
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Membrane potential Membrane potential refers to the net difference in charge on each side of a selectively permeable membrane due to an imbalance of cations and anions. This difference has the potential to become electrical energy (current) which is produced when ions move down an electrochemical gradient. In the body, a membrane potential exists between the intracellular fluid and the extracellular fluid (ie almost all cells and the extracellular fluid surrounding it). Membrane potential is measured in milivolts (mV) in the body. It is always measured with the inside (ICF) relative to the outside (ECF).
Physiological changes in pregnancy
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Symptoms of pregnancy Pregnancy leads to many symptoms which would be considered an illness or disease at other times. These symptoms are caused by hormonal changes which help create an optimum environment for the fetus and to support the increasing needs of the mother and child. Symptoms shown in pregnancy include anaemia, breathlessness, pelvic pain, swollen legs, increased urination, flushing, nausea, backaches, increased pigmentation, swollen or tender breast, and tiredness. Effects of fetus to the respiratory system There is an increased utilization of oxygen due to the fetus. (about 20% at term) The expanding uterus limits the movement of the maternal diaphragm. This leads to feelings of breathlessness
Fetal circulation
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Fetal circulation As a fetus’s lungs, kidneys and GI tract are not functional before birth, the fetus receives oxygen, nutrients and removes wastes via the maternal circulatory system. This is done through the placenta where the maternal blood and the fetus’ blood are bought in close contact. Due to a fetus’ different oxygen needs and supply, the fetal circulation is adapted such that unused parts of the body do not receive excess blood whist other areas are depleted. This is occurs via 3 shunts: l Ductus venosus l Foramen ovale l Ductus Arteriosus
The dermatomes
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The cranial nerves The face is supplied by 3 branches of the tri gemminal nerve, and the back of the head is supplied by the cervical nerves. the spinal nerves C1-8 supplies the back of head and upper limbs C3-4 supplies the shoulder. C6, 7 and 8 supplies the hand from lateral to medial. T1-12 supplies the trunk T1 supplies the anterior medial surface of the arm. T4 is at the level of the nipples and T10 is at the level of the umbellicus L1-5 supplies the anterior leg and lower back. L2 supplies the pocket shaped areas L 3 supplies the knee S1 supplies the lateral side of the foot S2 supplies the back of leg S3 supplies the penis.
Osteoporosis and osteomalacia
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Control of serum calcium levels Bone is made up of hydroyapatite and a fibrous framework. Ca 3 (PO 4 ) 2 + Ca(OH) 2 à Ca 5 (PO 4 ) 3 (OH) Tricalcium phosphate + calcium hydroxide à hydroxyapatite Bone is maintained by osteo C lasts which ‘ C rush’/breaks down bone and osteo B lasts which B uild bone. The breaking down of old bone is also called bone resorption and the formation of new bone is called ossification . This constant relaying of bone helps reshape bones, and repair micro-damages as well as injuries. This continuous bone remodeling is called bone turnover. In adults the rates of bone formation and bone breakdown is usually almost equal. Calcium levels in the body are regulated by parathyroid hormone, calcitonin and vitamin D. The levels of calcium in blood is carefully controlled in the short term, and the total levels of calcium in the body also needs to be constantly maintained. The regulation of calcium is mainly carried out by Parathyroid hormone, whi...
Brachial Plexus (and the story of Armmu)
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The brachial plexus is a network of somatic nerves formed by the anterior rami of C5-8 and part of the anterior ramus of T1. It originates from the neck and passes laterally over the first rib and down into the axilla. Major nerves innervating the upper limb originates from the brachial plexus. The nerves are posterior to the subclavian artery proximally and surrounds the axillary artery more distally.
anterior abdominal wall
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Abdominal muscles Transversus abdominis Rectus abdominis Internal oblique External oblique The rectus abdominis is surrounded by a aponeuroses - tendinous sheets- called the sheath of the rectus abdominis. These extend from the other three muscles of the abdomen. The flat abdominal muslces (transversus abdominis, internal oblique and external oblique) arise from the lateral sides of the abdomen and its tendons join at the midline forming a line of fibrous tissue called the linea alba . The fibres of the external oblique rolls inwards between the anterior superior iliac spine and the pubis forming the inguinal ligament . The abdominal muscles compress the abdomen during expiration, urination and defecation and help maintain posture. S ophie's fat C at S at I n between E lite IT T echies E ating P opcorn. [Skin,(fat)Camper's fascia, Scrapa's fascia, Investing fascia (between), External oblique, Int...
Calcium regulation
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When calcium is low: The parathyroid gland secretes parathyroid hormone Parathyroid hormone increases osteoclast activity and more calcium and phosphate is released into the blood stream from the bone. Parathyroid hormone also increases secretion of phosphates by the kidneys, and also increases calcium reabsorption. This causes an instant increase in serum calcium levels. Parathyroid hormone also works on the kidney to increase the rate of vitamin D activation. Activated vitamin D (calcitriol) is needed for calcium absorption. Increased calcitriol levels increase the absorption of calcium from the terminal ileum of the small intestines. This leads to an increase in serum calcium and restores the total amount of calcium in the body in the long term. calcitriol also increases bone sensitivity to parathyroid hormone further increasing amount of calcium in blood. The parathyroid glands are sensitive to changes in serum calcium, therefor...
Ectopic pregnancies
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An ectopic pregnancy refers to a pregnancy which starts outside the womb. This is usually in the uterine tubes, but may include the gastric area, the ovaries or the cervix. Ectopic pregnancies are usually caused by factors which prevent or slow the oocyte from arriving at the womb. This includes physical blockages, and hormonal factors. Scarring of the uterine tubes from previous pelvic infections may increase the risk of ectopic pregnancies. Ectopic pregnancies may result in the rupture of the uterine tubes and severe haemorrhage during the first 8 weeks of gestation which may be fatal to both mother and child. Symptoms of ectopic pregnancies include abnormal vaginal bleeds, amennhorea (lack of menstruation), breast tenderness, Lower back pain, pain on one side of the pelvis, nausea or pain in lower abdomen or pelvic area. If left untreated symptoms may extend to fainting, sharp pain in the abdomen and shoulders, and pressure on the rectum. Internal bleeding may also lead to s...
The Female Reproductive System
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The female reproductive system consists of the ovaries, uterine tubes, the uterus, vagina and external organs collectively called the vulva. The mammary glands are also considered a part of the reproductive system. The ovaries The ovaries are the female gonads. They are the size of an unshelled almonds and have the same embryonic origins as testes. The ovaries produce gametes and hormones. The ovaries are found on either side of the uterus, in the superior side of the pelvic cavity. It is suspended in place by a series of ligaments. This includes the mesovarium derived from the broad ligament of the uterus, the ovarian ligament and the suspensory ligament . Each ovary contains a hilum where vessels enter, and where the mesovarium attatches. Ovaries consist of the germinal epithelium made up of epithelial cells, over a capsule of connective tissue called the tunica albuginea . Beneath this lies the ovarian cortex , which contains many ovarian follicles surrounded by dense ...