Terms of Position, Direction and the main planes of human body

The Diagram below shows the chief terms of position and direction and the main planes of reference in the body.

*A convention whereby the body is erect, with the head, eyes, and toes directed forward and the upper limbs by the side and held so that the palms of the hands face forward "unlike the figure at left " . It is often necessary, however, to describe the position of the viscera also in the recumbent posture, because this is a posture in which patients are frequently examined clinically. 

*The median plane is an imaginary vertical plane of section that passes longitudinally through the body and divides it into right and left halves. The median plane intersects the surface of the front and back of the body at what are called the anterior and posterior median lines. It is a common error, however, to refer to the" midline" when the median plane is meant.

Any vertical plane through the body that is parallel with the median plane is called a sagittal plane. The sagittal planes are named after the sagittal suture of the skull, to which they are parallel. The term "parasagittal" is redundant: anything parallel with a sagittal plane is still sagittal.

The term horizontal plane refers to a plane at a right angle to both the median and coronal planes: it separates the body into superior and inferior parts. This is often termed an axial plane, particularly in radiology.

The term transverse means at a right angle to the longitudinal axis of a structure. Thus, a transverse section through an artery is not necessarily horizontal. A transverse section through the hand is horizontal, whereas a transverse section through the foot is coronal !!

The suffix "-ad" is sometimes added to a positional term to indicate the idea of motion. Thus, cephalad means proceeding toward the head. Such terms are useful occasionally in describing growth processes, but their application is best limited.

the Stomach:Arterial supply

The arteries that supply the stomach are branches of the celiac trunk . This is the first unpaired branch of the abdominal aorta, arising just after the aorta passes behind the diaphragm.
The branches of the celiac artery are three:

1. left gastric
2. splenic
3. common hepatic

Good Mnemonics for Thenar and hypothenar muscles

FAO (Flex, Oppose, Abduct)

thenar:
Flexor pollicis brevis, Opponens pollicis, Abductor pollicis brevis. 


hypothenar:
Flexor digiti minimi, Abductor digiti minimi, Opponens digiti minimi.

Diagram of Anterior anatomical relations of both kidney

The kidneys are retroperitoneal organs that are located in the perirenal retroperitoneal space with a longitudinal diameter of 10–12 cm and a latero-lateral diameter of 3–5 cm and a weight of 250–270 g.
In the supine position, the medial border of the normal kidney is much more anterior than the lateral border, The upper pole of each kidney is situated more posteriorly than the lower pole.

The right kidney,  anteriorly :

has a relation with the inferior surface of the liver with peritoneal interposition,and with the second portion of the duodenum without any peritoneal interposition since the second portion of the duodenum is retroperitoneal .
The left kidney, anteriorly :
has a relation with the pancreatic tail, the spleen, the stomach, the ligament of Treitz and small bowel, and with the left colic lexure and left colon . Over the left kidney, there are two important peritoneal relections, one vertical corresponding to the spleno-renal ligament (connected to
the gastro-diaphragmatic and gastrosplenic ligaments) and one horizontal corresponding to the transverse mesocolon.

Complete neuron cell diagram

Neurons can respond to stimuli and conduct impulses because a membrane potential is established across the cell membrane. In other words, there is an unequal distribution of ions (charged atoms) on the two sides of a nerve cell membrane. This can be illustrated with a voltmeter:

With one electrode placed inside a neuron and the other outside, the voltmeter is 'measuring' the difference in the distribution of ions on the inside versus the outside. And, in this example, the voltmeter reads -70 mV (mV = millivolts).
In other words, the inside of the neuron is slightly negative relative to the outside. This difference is referred to as the Resting Membrane Potential

ACC Atlas of Pathophysiology

Featuring 450 large full-color illustrations, this comprehensive atlas shows how more than 200 disorders can disrupt the human body’s equilibrium. It is designed to help healthcare professionals visualize disease processes, understand the rationales for clinical interventions, and explain to patients how diseases develop and progress.

Introductory chapters illustrate basic pathophysiologic concepts including cells, cancer, infection, genetics, and fluids and electrolytes. Twelve chapters organized by body system cover all major diseases, with illustrations, charts, and brief text on causes, pathophysiology, signs, symptoms, diagnostic tests, and treatment.

This Third Edition includes eight new disease entries and updated information throughout. A new icon, Complications, highlights the typical progression of untreated disease.

SLUG BAM: Muscarinic effects of Acetylcholine

Acetylcholine acts on two vastly different classes of receptors - nicotinic receptors (with two subtypes, one at the neuromuscular junction of skeletal muscle, the other within ganglia and the CNS), and muscarinic receptors (widely distributed within both peripheral and central nervous systems).

**Muscarinic effects SLUG BAM:

• Salivation/ Secretions/ Sweating
• Lacrimation
• Urination
• Gastrointestinal upset
• Bradycardia/ Bronchoconstriction/ Bowel movement
• Abdominal cramps/ Anorexia
• Miosis

Neural transmission in the nodes of Ranvier

The nodes of Ranvier increase the efficiency of neural transmission by means of which of the following?

• a.Decelerating the closing of Na -gated channels
• b.Enhancing myelination of the internodal segment
• c.Sequestration of Na entry into the axon
• d.Multiple firings due to local ionic currents around the node
• e.Decreasing threshold for the action potential

 The answer is  (c ).

The nodes of Ranvier increase the efficiency of nodal conduction because of restriction (sequestration) of energy–dependent Na influx to the node. The nodes of Ranvier represent
the space between adjacent units of myelination.
This area is bare in the CNS, whereas in the PNS the axons in the nodes are partially covered by the cytoplasmic tongues of adjacent Schwann cells. Most of the Na -gated channels are located in the bare areas. Therefore, spread of depolarization from the nodal region along the axon occurs until it reaches the next node.
This is often described as a series of jumps from node to node, or saltatory conduction.

The Physiology of Stress in human

the stress respond

In stress (as in threatening situations that we are unable to cope with) messages are carried along neurones from the cerebral cortex (where the thought processes occur) and the limbic system to the Hypothalamus.

The Anterior Hypothalamus produces sympathetic arousal of the Autonomic Nervous System (ANS). The ANS is an automatic system that controls the heart, lungs, stomach, blood vessels and glands. Due to its action we do not need to make any conscious effort to regulate our breathing or heart beat. The ANS consists of : the sympathetic nervous system and the parasympathetic nervous system. Essentially, the parasympathetic nervous system conserves energy levels. It increases bodily secretions such as tears, gastric acids, mucus and saliva which help to defend the body and help digestion. Chemically, the parasympathetic system sends its messages by a neurotransmitter acetylcholine which is stored at nerve endings.

Unlike the parasympathetic nervous system which aids relaxation, the sympathetic nervous system prepares the body for action. In a stressful situation, it quickly does the following:

* Increases strength of skeletal muscles
* Decreases blood clotting time
* Increases heart rate
* Increases sugar and fat levels
* Reduces intestinal movement
* Inhibits tears, digestive secretions.
* Relaxes the bladder
* Dilates pupils
* Increases perspiration
* Increases mental activity
* Inhibits erection/vaginal lubrication
* Constricts most blood vessels but dilates those in heart/leg/arm muscles

The main sympathetic neurotransmitter is noradrenaline which is released a the nerve endings. The stress response also includes the activity of the adrenal, pituitary and thyroid glands.

The two adrenal glands are located one on top of each kidney. the adrenal medulla is connected to the sympathetic nervous system by nerves. Once the latter system is in action it instructs the adrenal medulla to produce adrenaline and noradrenaline (catecholamines) which are released into the blood supply. The adrenaline prepares the body for flight and the noradrenaline prepares the body for fight. They increase both the heart rate, and the pressure at which the blood leaves the heart; they dilate bronchial passages and dilate coronary arteries; skin blood vessels constrict and there is an increase in metabolic rate. Also gastrointestinal system activity reduces which leads to a sensation of butterflies in the stomach.

Lying close to the hypothalamus in the brain the pituitary gland. In a stressful situation, the anterior hypothalamus activates the pituitary. The pituitary releases adrenocorticotrophic hormone (ACTH) into the blood which then activates the outer part of the adrenal gland, the adrenal cortex. This then synthesises cortisol which increases arterial blood pressure, mobilises fats and glucose from the adipose (fat) tissues, reduces allergic reactions, reduces inflammation and can decrease lymphocytes that are involved in dealing with invading particles or bacteria. Consequently, increased cortisol levels over a prolonged period of time lowers the efficiency of the immune system. The adrenal cortex releases aldosterone which increases blood volume and subsequently blood pressure. Unfortunately, prolonged arousal over a period of time due to stress can lead to essential hypertension.
the pituatary
also releases thyroid stimulating hormone which stimulates the thyroid gland, to secrete thyroxin. Thyroxin increases the metabolic rate, raises blood sugar levels, increases respiration/heart rate/blood pressure/and intestinal motility. Increased intestinal motility can lead to diarrhoea. (It is worth noting that an over-active thyroid gland under normal circumstances can be a major contributory factor in anxiety attacks. This would normally require medication.)

The pituitary also releases oxytocin and vasopressin which contract smooth muscles such as the blood vessels. Oxytocin causes contraction of the uterus. Vasopressin increases the permeability of the vessels to water therefore increasing blood pressure. It can lead to contraction of the intestinal musculature.

for many people they perceive everyday of their life as stressful. Unfortunately, the prolonged effect of the stress response is that the body's immune system is lowered and blood pressure is raised which may lead to essential hypertension and headaches. The adrenal gland may malfunction which can result in tiredness with the muscles feeling weak; digestive difficulties with a craving for sweet, starchy food; dizziness; and disturbances of sleep.

Highest oxygen content in Fetal blood

Fetal blood from the placenta is about 80% oxygenated. However, mixture with unoxygenated blood at various points reduces the oxygen content.Which of the following fetal vessels contains blood with the highest oxygen content?
A.Abdominal aorta
B. Common carotid arteries
C.Ductus arteriosus
D.Pulmonary artery
E.Pulmonary vein.

the ANSWER B
Blood from the placenta in the umbilical cord is about 80% oxygenated. Mixture with unoxygenated blood from the vitelline veins and the inferior vena cava reduces the oxygen content somewhat. However, this stream with relatively high oxygen content is directed by the valve of the inferior vena cava directly through the foramen ovale into the left atrium. This prevents admixture with oxygen-depleted blood entering the right atrium from the superior vena cava.

Thus, the oxygen-saturated blood entering the left ventricle and pumped into the aortic arch, subclavian arteries, and common carotid arteries has the highest oxygen content. The oxygen depleted blood from the superior vena cava is directed into the right ventricle and then to the pulmonary trunk. Although a small portion of this flow passes through the lungs (where any residual oxygen is extracted by the tissue of the non-respiring lung), most is shunted into the thoracic aorta via the ductus arteriosus and thereby lowers the oxygen content of that vessel. This occurs distal to the origins of the carotid arteries and ensures that the rapidly developing brain has the best oxygen supply. The pattern of blood supply in the fetus and the changes that occur at birth are shown in the following figures.

Synovial joint:Blood and nerve supply

The blood supply of a synovial joint is derived from the arteries sharing in the anastomosis around the joint.And the nerve supply of a synovial joint is derived from the muscles which act on the joint ,best expressed by Hilton in 1863:
"The same trunks of nerves, whose branches supply the groups of muscles moving a joint, furnish also a distribution of nerves to the skin over the insertions of the same muscles; and what at this moment more especially merits our attention-the interior of the joint receives its nerves from the same source."

proprioceptive fibers endings in the capsule and ligaments are very sensitive to position and movement. Their central connections are such that they are concerned with the reflex control of posture and locomotion and the detection of position and movement.

This diagram shows the artery supplying the epiphysis, joint capsule, and synovial membrane. The nerve that contains1. sensory (mostly pain) fibers from the capsule and synovial membrane,2. autonomic (postganglionic sympathetic) fibers to blood vessels,3. sensory (pain) fibers from the adventitia of blood vessels.