The pterygopalatine ganglion is a parasympathetic ganglion found in the pterygopalatine fossa. It is innervated by the greater petrosal nerve; the flow of blood to the nasal mucosa, in particular the venous plexus of the conchae, is regulated by the pterygopalatine ganglion and heats or cools the air in the nose. It is one of four parasympathetic ganglia of the head and neck, the others being the submandibular ganglion, otic ganglion, ciliary ganglion; the pterygopalatine ganglion, the largest of the parasympathetic ganglia associated with the branches of the maxillary nerve, is placed in the pterygopalatine fossa, close to the sphenopalatine foramen. It is triangular or heart-shaped, of a reddish-gray color, is situated just below the maxillary nerve as it crosses the fossa; the pterygopalatine ganglion supplies the lacrimal gland, paranasal sinuses, glands of the mucosa of the nasal cavity and pharynx, the gingiva, the mucous membrane and glands of the hard palate. It communicates anteriorly with the nasopalatine nerve.
It receives a sensory, a parasympathetic, a sympathetic root. Its sensory root is derived from two sphenopalatine branches of the maxillary nerve, its parasympathetic root is derived from the nervus intermedius through the greater petrosal nerve. In the pterygopalatine ganglion, the preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve synapse with neurons whose postganglionic axons and secretory fibers are distributed with the deep branches of the trigeminal nerve to the mucous membrane of the nose, soft palate, uvula, roof of the mouth, upper lip and gums, upper part of the pharynx, it sends postganglionic parasympathetic fibers to the lacrimal nerve via the zygomatic nerve, a branch of the maxillary nerve, which arrives at the lacrimal gland. The nasal glands are innervated with secretomotor from the greater petrosal nerve; the palatine glands are innervated by the nasopalatine, greater palatine nerve and lesser palatine nerves. The pharyngeal nerve innervates pharyngeal glands.
These are all branches of maxillary nerve. The ganglion consists of sympathetic efferent fibers from the superior cervical ganglion; these fibers, from the superior cervical ganglion, travel through the carotid plexus, through the deep petrosal nerve. The deep petrosal nerve joins with the greater petrosal nerve to form the nerve of the pterygoid canal, which passes through the pterygoid canal before entering the ganglion. Orbital branches Nasopalatine nerve Greater palatine nerve Lesser palatine nerve Medial and Lateral Posterior Superior and Posterior Inferior Nasal Branches Pharyngeal branch of maxillary nerve This article incorporates text in the public domain from page 891 of the 20th edition of Gray's Anatomy synd/2132 at Who Named It? cranialnerves at The Anatomy Lesson by Wesley Norman
Anatomical terminology is a form of scientific terminology used by anatomists and health professionals such as doctors. Anatomical terminology uses many unique terms and prefixes deriving from Ancient Greek and Latin; these terms can be confusing to those unfamiliar with them, but can be more precise, reducing ambiguity and errors. Since these anatomical terms are not used in everyday conversation, their meanings are less to change, less to be misinterpreted. To illustrate how inexact day-to-day language can be: a scar "above the wrist" could be located on the forearm two or three inches away from the hand or at the base of the hand. By using precise anatomical terminology such ambiguity is eliminated. An international standard for anatomical terminology, Terminologia Anatomica has been created. Anatomical terminology has quite regular morphology, the same prefixes and suffixes are used to add meanings to different roots; the root of a term refers to an organ or tissue. For example, the Latin names of structures such as musculus biceps brachii can be split up and refer to, musculus for muscle, biceps for "two-headed", brachii as in the brachial region of the arm.
The first word describes what is being spoken about, the second describes it, the third points to location. When describing the position of anatomical structures, structures may be described according to the anatomical landmark they are near; these landmarks may include structures, such as the umbilicus or sternum, or anatomical lines, such as the midclavicular line from the centre of the clavicle. The cephalon or cephalic region refers to the head; this area is further differentiated into the cranium, frons, auris, nasus and mentum. The neck area is called cervical region. Examples of structures named according to this include the frontalis muscle, submental lymph nodes, buccal membrane and orbicularis oculi muscle. Sometimes, unique terminology is used to reduce confusion in different parts of the body. For example, different terms are used when it comes to the skull in compliance with its embryonic origin and its tilted position compared to in other animals. Here, Rostral refers to proximity to the front of the nose, is used when describing the skull.
Different terminology is used in the arms, in part to reduce ambiguity as to what the "front", "back", "inner" and "outer" surfaces are. For this reason, the terms below are used: Radial referring to the radius bone, seen laterally in the standard anatomical position. Ulnar referring to the ulna bone, medially positioned when in the standard anatomical position. Other terms are used to describe the movement and actions of the hands and feet, other structures such as the eye. International morphological terminology is used by the colleges of medicine and dentistry and other areas of the health sciences, it facilitates communication and exchanges between scientists from different countries of the world and it is used daily in the fields of research and medical care. The international morphological terminology refers to morphological sciences as a biological sciences' branch. In this field, the form and structure are examined as well as the changes or developments in the organism, it is functional.
It covers the gross anatomy and the microscopic of living beings. It involves the anatomy of the adult, it includes comparative anatomy between different species. The vocabulary is extensive and complex, requires a systematic presentation. Within the international field, a group of experts reviews and discusses the morphological terms of the structures of the human body, forming today's Terminology Committee from the International Federation of Associations of Anatomists, it deals with the anatomical and embryologic terminology. In the Latin American field, there are meetings called Iberian Latin American Symposium Terminology, where a group of experts of the Pan American Association of Anatomy that speak Spanish and Portuguese and studies the international morphological terminology; the current international standard for human anatomical terminology is based on the Terminologia Anatomica. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998.
It supersedes Nomina Anatomica. Terminologia Anatomica contains terminology for about 7500 human gross anatomical structures. For microanatomy, known as histology, a similar standard exists in Terminologia Histologica, for embryology, the study of development, a standard exists in Terminologia Embryologica; these standards specify accepted names that can be used to refer to histological and embryological structures in journal articles and other areas. As of September 2016, two sections of the Terminologia Anatomica, including central nervous system and peripheral nervous system, were merged to form the Terminologia Neuroanatomica; the Terminologia Anatomica has been perceived with a considerable criticism regarding its content including coverage and spelling mistakes and errors. Anatomical terminology is chosen to highlight the relative location of body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician might describe a tumor as "superficial to" a deeper body structure.
Anatomical terms used to describe location
A reflex, or reflex action, is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex is made possible by neural pathways called reflex arcs which can act on an impulse before that impulse reaches the brain; the reflex is an automatic response to a stimulus that does not receive or need conscious thought. Myotatic reflexes The myotatic reflexes, provide information on the integrity of the central nervous system and peripheral nervous system. Decreased reflexes indicate a peripheral problem, lively or exaggerated reflexes a central one. A stretch reflex is the contraction of a muscle in response to its lengthwise stretch. Biceps reflex Brachioradialis reflex Extensor digitorum reflex Triceps reflex Patellar reflex or knee-jerk reflex Ankle jerk reflex While the reflexes above are stimulated mechanically, the term H-reflex refers to the analogous reflex stimulated electrically, tonic vibration reflex for those stimulated to vibration. A tendon reflex is the contraction of a muscle in response to striking its tendon.
The Golgi tendon reflex is the inverse of a stretch reflex. Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes; these automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place. They include: Asymmetrical tonic neck reflex Palmomental reflex Moro reflex known as the startle reflex Palmar grasp reflex Rooting reflex Sucking reflex Symmetrical tonic neck reflex Tonic labyrinthine reflex Other reflexes found in the central nervous system include: Abdominal reflexes Gastrocolic reflex Anocutaneous reflex Baroreflex Cough reflex Cremasteric reflex Diving reflex Muscular defense Photic sneeze reflex Scratch reflex Sneeze Startle reflex Withdrawal reflex Crossed extensor reflexMany of these reflexes are quite complex requiring a number of synapses in a number of different nuclei in the CNS. Others of these involve just a couple of synapses to function. Processes such as breathing and the maintenance of the heartbeat can be regarded as reflex actions, according to some definitions of the term.
In medicine, reflexes are used to assess the health of the nervous system. Doctors will grade the activity of a reflex on a scale from 0 to 4. While 2+ is considered normal, some healthy individuals are hypo-reflexive and register all reflexes at 1+, while others are hyper-reflexive and register all reflexes at 3+. List of reflexes All-or-none law Automatic behavior Conditioned reflex Instinct Jumping Frenchmen of Maine Voluntary action Preflexes
The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity, involved in smell. In humans, it measures 9 cm2 and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils; the olfactory epithelium is the part of the olfactory system directly responsible for detecting odors. Olfactory epithelium consists of four distinct cell types: Olfactory sensory neurons Supporting cells Basal cells Brush cells The olfactory sensory neurons of the olfactory epithelium are bipolar neurons; the apical poles of these neurons express odorant receptors on non-motile cilia at the ends of the dendritic knob, which extend out into the airspace to interact with odorants. Odorant receptors bind odorants in the airspace, which are made soluble by the serous secretions from olfactory glands located in the lamina propria of the mucosa; the axons of the olfactory sensory neurons congregate to form the olfactory nerve. Once the axons pass through the cribriform plate, they terminate and synapse with the dendrites of mitral cells in the glomeruli of the olfactory bulb.
Analogous to neural glial cells, the supporting cells are non-neural cells in the olfactory epithelium that are located in the apical layer of the pseudostratified ciliated columnar epithelium. There are two types of supporting cells in the olfactory epithelium: sustentacular cells and microvillar cells; the sustentacular cells function as physical support for the olfactory epithelium. Microvillar cells are another class of supporting cells that are morphologically and biochemically distinct from the sustentacular cells, arise from a basal cell population that expresses c-Kit. Resting on or near the basal lamina of the olfactory epithelium, basal cells are stem cells capable of division and differentiation into either supporting or olfactory cells. While some of these basal cells divide a significant proportion remain quiescent and replenish olfactory epithelial cells as needed; this leads to the olfactory epithelium being replaced every 6–8 weeks. Basal cells can be divided on the basis of their cellular and histological features into two populations: the horizontal basal cells, which are dividing reserve cells that express p63.
A brush cell is a microvilli-bearing columnar cell with its basal surface in contact with afferent nerve endings of the trigeminal nerve and is specialized for transduction of general sensation. Tubuloalveolar serous secreting glands lying in the lamina propria of the mucosa; these glands deliver a proteinaceous secretion via ducts onto the surface of the mucosa. The role of the secretions are to dissolve odiferous substances for the bipolar neurons. Constant flow from the olfactory glands allows old odors to be washed away; the olfactory epithelium derives from two structures during embryonic development: the olfactory placode, long believed to be its sole origin. The embryonic olfactory epithelium consists of fewer cell types than in the adult, including apical and basal progenitor cells, as well as immature olfactory sensory neurons. Early embryonic neurogenesis relies on the apical cells, while stage embryonic neurogenesis and secondary neurogenesis in adults relies on basal stem cells; the axons of the immature olfactory sensory neurons, along with a mixed population of migratory cells, including immature olfactory ensheathing cells and gonadotropin-releasing hormone neurons form a “migratory mass” that travels towards the olfactory bulb.
At the end of the embryonic stage, the epithelium develops into a pseudostratified columnar epithelium and begins secondary neurogenesis. Placodes are transient, focal aggregations of ectoderm located in the developmental region of future vertebrate head, give rise to sensory organs. Early cranial sensory placodes are marked by expression of Six1, part of the Six family of transcription factors that regulate preplacodal ectoderm specification; the olfactory placode forms as two thickenings of non-neural region of embryonic ectoderm. In mice, the olfactory placode derives from an anterior portion of the neural tube, ~9-9.5 days into development and not long after the closure of the neural plate. Development of the olfactory placode requires the presence underlying neural crest-derived mesenchymal tissue; the specification of the olfactory placode tissue involves signaling of multiple gene networks, beginning with signals from bone morphogenetic proteins, retinoic acid, fibroblast growth factor FGF8.
The resulting regulated downstream expression of transcription factors, such as Pax6, Dlx3, Sox2, others, within the presumptive olfactory placode are crucial for sub-regionalization within the future olfactory epithelium and is responsible for the diversity of cells that compose the future epithelium. Similar to the other embryonic placodes, the olfactory placode gives rise to both neural and non-neural structures resulting in the formation of the nasal epithelium; the specification of neural versus non-neural tissue involves signals both within the olfactory placode, between the olfactory placode and the underlying mesenchymal compartment. Continued signaling by BMP, FGF, RA, the morphogens that induced placode formation, collectively coordinate the patterning of olfactory placode tissue into the future distinct cell types that make up the olfactory epithelium; the cell types derived from the olfactory placode include: Neural: olfactory sensory neurons, LHRH-secreting neu
Vertebrates comprise all species of animals within the subphylum Vertebrata. Vertebrates represent the overwhelming majority of the phylum Chordata, with about 69,276 species described. Vertebrates include the jawless fishes and jawed vertebrates, which include the cartilaginous fishes and the bony fishes; the bony fishes in turn, cladistically speaking include the tetrapods, which include amphibians, reptiles and mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, at up to 33 m. Vertebrates make up less than five percent of all described animal species; the vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, the lampreys, do. Hagfish do, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as "Craniata" when discussing morphology. Molecular analysis since 1992 has suggested that hagfish are most related to lampreys, so are vertebrates in a monophyletic sense.
Others consider them a sister group of vertebrates in the common taxon of craniata. The word vertebrate derives from the Latin word vertebratus. Vertebrate is derived from the word vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it and the gastrointestinal tract below. In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body; the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. The defining characteristic of a vertebrate is the vertebral column, in which the notochord found in all chordates has been replaced by a segmented series of stiffer elements separated by mobile joints. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon and coelacanth.
Jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills; the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch; the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their chordate relatives have more than 50 pairs of gills. In amphibians and some primitive bony fishes, the larvae bear external gills, branching off from the gill arches; these are reduced in adulthood, their function taken over by the gills proper in fishes and by lungs in most amphibians. Some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish being irrevocably lost early in the evolution of tetrapods.
While the more derived vertebrates lack gills, the gill arches form during fetal development, form the basis of essential structures such as jaws, the thyroid gland, the larynx, the columella and, in mammals, the malleus and incus. The central nervous system of vertebrates is based on a hollow nerve cord running along the length of the animal. Of particular importance and unique to vertebrates is the presence of neural crest cells; these are progenitors of stem cells, critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the nerve cord during development, initiate the formation of neural ganglia and structures such as the jaws and skull; the vertebrates are the only chordate group to exhibit cephalisation, the concentration of brain functions in the head. A slight swelling of the anterior end of the nerve cord is found in the lancelet, a chordate, though it lacks the eyes and other complex sense organs comparable to those of vertebrates.
Other chordates do not show any trends towards cephalisation. A peripheral nervous system branches out from the nerve cord to innervate the various systems; the front end of the nerve tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles: The prosencephalon and rhombencephalon, further differentiated in the various vertebrate groups. Two laterally placed eyes form around outgrowths from the midbrain, except in hagfish, though this may be a secondary loss; the forebrain is well developed and subdivided in most tetrapods, while the midbrain dominates in many fish and some salamanders. Vesicles of the forebrain are paired, giving rise to hemispheres like the cerebral hemispheres in mammals; the resulting anatomy of the central nervous system, with a single hollow nerve cord topped by a series of vesicles, is unique to vertebrates. All invertebrates with well-developed brains, such as insects and squids, have a ventral rather than dorsal system of ganglions, with a split brain stem running on each side of the mouth or gut.
Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw
Anosmia is the inability to perceive odor or a lack of functioning olfaction—the loss of the sense of smell. Anosmia may be temporary. Anosmia is due to a number of factors, including an inflammation of the nasal mucosa, blockage of nasal passages or a destruction of one temporal lobe. Inflammation is due to chronic mucosa changes in the paranasal sinus lining and the middle and superior turbinates; when anosmia is caused by inflammatory changes in the nasal passageways, it is treated by reducing inflammation. It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time, in some cases by ciliopathy including ciliopathy due to primary ciliary dyskinesia. Many patients may experience unilateral anosmia as a result of minor head trauma; this type of anosmia is only detected if both of the nostrils are tested separately. Using this method of testing each nostril separately will show a reduced or completely absent sense of smell in either one nostril or both, something, not revealed if both nostrils are tested.
A related term, refers to a decreased ability to smell, while hyperosmia refers to an increased ability to smell. Some people may be anosmic for one particular odor; this is known as "specific anosmia". The absence of the sense of smell from birth is called congenital anosmia. Anosmia can have a number of harmful effects. Patients with sudden onset anosmia may find food less appetizing, though congenital anosmics complain about this, none report a loss in weight. Loss of smell can be dangerous because it hinders the detection of gas leaks and spoiled food; the common view of anosmia as trivial can make it more difficult for a patient to receive the same types of medical aid as someone who has lost other senses, such as hearing or sight. Losing an established and sentimental smell memory has been known to cause feelings of depression. Loss of olfaction may lead to the loss of libido, though this does not apply to congenital anosmics. People who have congenital anosmia report that they pretended to be able to smell as children because they thought that smelling was something that older/mature people could do, or did not understand the concept of smelling but did not want to appear different from others.
When children get older, they realize and report to their parents that they do not possess a sense of smell to the surprise of their parents. A study done on patients suffering from anosmia found that when testing both nostrils, there was no anosmia revealed; this demonstrated. A temporary loss of smell can be caused by infection. In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the olfactory nerve or damage to brain areas that process smell; the lack of the sense of smell at birth due to genetic factors, is referred to as congenital anosmia. Family members of the patient suffering from congenital anosmia are found with similar histories. Anosmia may occasionally be an early sign of a degenerative brain disease such as Parkinson's disease and Alzheimer's disease. Another specific cause of permanent loss could be from damage to olfactory receptor neurons because of use of certain types of nasal spray.
To avoid such damage and the subsequent risk of loss of smell, vasoconstricting nasal sprays should be used only when necessary and for only a short amount of time. Non-vasoconstricting sprays, such as those used to treat allergy-related congestion, are safe to use for prescribed periods of time. Anosmia can be caused by nasal polyps; these polyps are found in people with histories of sinusitis & family history. Individuals with cystic fibrosis develop nasal polyps. Amiodarone is a drug used in the treatment of arrhythmias of the heart. A clinical study performed demonstrated. Although rare, there was a case in which a 66-year-old male was treated with Amiodarone for ventricular tachycardia. After the use of the drug he began experiencing olfactory disturbance, however after decreasing the dosage of Amiodarone, the severity of the anosmia decreased accordingly hence correlating the use of Amiodarone to the development of anosmia. Anosmia can be diagnosed by doctors by using acetylcysteine tests.
Doctors will begin with a detailed elicitation of history. The doctor will ask for any related injuries in relation to anosmia which could include upper respiratory infections or head injury. Psychophysical Assessment of order and taste identification can be used to identify anosmia. A nervous system examination is performed to see; the diagnosis as well as the degree of impairment can now be tested much more efficiently and than before thanks to "smell testing kits" that have been made available as well as screening tests which use materials that most clinics would have. After accidents, there is a change in a patient's sense of smell. Particular smells that were present before are no longer
Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time; when used without qualification, "weather" is understood to mean the weather of Earth. Weather is driven by air pressure and moisture differences between one place and another; these differences can occur due to the sun's angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations: the Hadley Cell, the Ferrel Cell, the Polar Cell, the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow.
Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth's surface, temperatures range ±40 °C annually. Over thousands of years, changes in Earth's orbit can affect the amount and distribution of solar energy received by the Earth, thus influencing long-term climate and global climate change. Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes, as most atmospheric heating is due to contact with the Earth's surface while radiative losses to space are constant. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location; the Earth's weather system is a chaotic system. Human attempts to control the weather have occurred throughout history, there is evidence that human activities such as agriculture and industry have modified weather patterns. Studying how the weather works on other planets has been helpful in understanding how weather works on Earth.
A famous landmark in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies. A star's corona is being lost to space, creating what is a thin atmosphere throughout the Solar System; the movement of mass ejected from the Sun is known as the solar wind. On Earth, the common weather phenomena include wind, rain, snow and dust storms. Less common events include natural disasters such as tornadoes, hurricanes and ice storms. All familiar weather phenomena occur in the troposphere. Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood. Weather occurs due to air pressure and moisture differences between one place to another; these differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. In other words, the farther from the tropics one lies, the lower the sun angle is, which causes those locations to be cooler due the spread of the sunlight over a greater surface.
The strong temperature contrast between polar and tropical air gives rise to the large scale atmospheric circulation cells and the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Weather systems in the tropics, such as monsoons or organized thunderstorm systems, are caused by different processes; because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December; this effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate.. The uneven solar heating can be due to the weather itself in the form of cloudiness and precipitation.
Higher altitudes are cooler than lower altitudes, which the result of higher surface temperature and radiational heating, which produces the adiabatic lapse rate. In some situations, the temperature increases with height; this phenomenon is known as an inversion and can cause mountaintops to be warmer than the valleys below. Inversions can lead to the formation of fog and act as a cap that suppresses thunderstorm development. On local scales, temperature differences can occur because different surfaces have differing physical characteristics such as reflectivity, roughness, or moisture content. Surface temperature differences in turn cause pressure differences. A hot surface warms the air above it causing it to expand and lower the density and the resulting surface air pressure; the resulting horizontal pressure gradient moves the air from higher to lower pressure regions, creating a wind, the Earth's rotation causes deflection of this air flow due to the Coriolis effect. The simple systems thus formed can display emergent behaviour to produce more complex systems and thus other weather phenomena.
Large scale examples include the Hadley cell while a small