Y khoa, y dược - Chapter 11: The senses

 Chapter 11The Senses Introduction This presentation focuses on several organs that collectively provide the individual with their insight into the outside world. The ability to ‘sense’ is a primitive function developed through thousands of years of evolutionary change. The senses are taken for granted by those with a fully functioning ability but for many a combination of congenital, degenerative, and acute pathologies result in a decreased ability in one or more of these functions. This can have major affects on the individuals ability to function, their mental health and the way they are perceived and treated by the society they live in.The Eye (Sight) The eyes are only one of a number of structures involved in achieving the sense of vision, these include:The eyelidsThe lacrimal glandsThe extrinsic muscles of eye movementThe eyelids are composed of very fine skin and muscle, connective tissue containing oil secreting sebaceous glands and the conjunctiva.The lacrimal gland is anatomically located laterally and superiorly within the eyes orbit. This gland works in unison with glandular cells to lubricate and moisten the eye. The EyeLateral Illustration & Anterior PhotographEye FunctioningThe function of the eyes centres on providing the individual with vision. Vision consists of several vital concurrent functions, the properties of which include brightness and colour. When vision is normal, seeing is so effortless that the individual functions that comprise vision are imperceptible.Vision is composed of three distant perceptions:FormsColoursMovement Central Interpretation The eyes must continually adapt to meet the external environment. In daylight the eye uses photopic vision.Colours are varied and easily distinguishable due to the action of three different types of cone cells that sense three respective bands of colour. Scotopic vision is the primary source of vision; since cone cells are nonfunctional in low light.Mesopic vision is a combination of photopic and scotopic vision. This combination effect results in an inaccurate visual acuity and colour discrimination with a resulting higher total sensitivity for the blue range of colours.Drugs Affecting The Eyes Many drugs can affect the eyes ability to function normally even when very low or therapeutic doses are given. Most of these drugs either dilate the pupil, known as mydriatics or constrict the pupil known as miotics.Miotics result in a constriction of the pupil by constricting muscles that surround the eye. Constriction of the eye can also be caused by metabolic disorders these include renal failure. Drugs that have a mydriatic affect simply result in a dilated pupil. Patient ScenarioGabrielle Downing a 29-year-old mother of two young children arrives at the GP surgery where you are on placement. Gabrielle has an emergency appointment with the practice nurse. Her presenting complaint is a two-day history of a red, inflamed and painful right eye. This morning her eye was stuck together and she has a sensation of grit in her eye. On examination her vital signs are normal for her age and she is apyrexial. Assessment & Analysis of Patient Presentation Ms Downing is presenting with the classic clinical symptoms of conjunctivitis, this centres on the physical presentation of an acute and non-traumatic red eye.Conjunctivitis can be defined as inflammation of the conjunctiva; the transparent membrane that covers the inner surface of the eyelid and most of the anterior surface of the eyeball. Because the conjunctiva has such an excellent nerve and blood supply it can become extremely swollen and painful when aggravated. The cause can very from localised infections through to allergic reactions. ConjunctivitisConjunctivitis can be caused by a multitude of organisms or varying stimuli. The most common presentation is bacterial infection caused by colonisation of the conjunctiva by pathogens such as Haemophilus influenzae, Streptococcus pneumoniae and Staphylococcus (Prodigy 2007). Infective conjunctivitis is associated with many underlying causes e.g. foreign bodies, scratches and direct entry through localised contamination i.e. rubbing the eye with dirty fingers.Clinically it is problematical to differentiate between a bacterial or viral cause The treatment centres on eradicating bacteria so that even if the infection is caused by a virus the administration of antibiotics will stop opportunistic bacterial proliferation. The Ears (Hearing) The ears are composed of three distinct sections;Outer earMiddle earInner earThe flexible external ear consists of the pinna, the external auditory meatus, auditory canal and the lateral surface of the eardrum – tympanic membrane. The outer ear canal is cartilaginous in its outer one third and bony in its inner two thirds. The outer third of this canal has a bony framework. The tympanic membrane separates the outer and middle ear. The inner ear consists of closed, fluid-filled spaces within the temporal bone. It contains the bony labyrinth, which includes three connected structures: the vestibule, the semicircular canals, and the cochlea. The vestibular part of the inner ear is concerned with balance; the cochlea is concerned with hearing The Inner Workings of the EarOverview There are 8,945,000 deaf or hard of hearing people in the United Kingdom. There are four levels of deafness, defined according to the quietest sound that can be heard:Mild deafness – can cause some difficulty following speech mainly in noisy situationsModerate deafness – difficulty following speech without a hearing aidSevere deafness – heavy reliance on lip reading, even with a hearing aidProfound deafness – BSL is usually the first or preferred language, or reliance on lip readingHard of hearing is used to describe people with a mild to severe hearing loss, usually used for people who have lost their hearing gradually. Clinical ScenarioJohn McNamara is an 18-year-old mechanic who had a sudden onset of right-sided ear pain two days ago. He took analgesia with good effect but the pain has continued. When John awoke this morning he noticed some discharge from his ear on the pillow and as he arose he realised his hearing was muffled, he does not have any problems walking and is not experiencing any loss of balance. John has attended the Health clinic where you are on placement and is assessed by yourself under the guidance of a practice nurse.John’s vital sign are recorded as: Respiratory rate 16 and regular, pulse rate 89 strong and regular, blood pressure 118/72, temperature 37.6.When inspected through otoscopy it is noted that the ear canal is inflamed and there is evidence of a dried discharge. The tympanic membrane is intact, although bulging.John has no previous medical history or allergies. He has recently suffered from what he calls flu like symptoms and still has nasal congestion and a sore throat Assessment and Analysis of Patient Presentation John McNamara is presenting with the classic signs and symptoms of an infection affecting the middle ear. His recent history of a possible viral infection affecting the upper respiratory tract is a frequent finding. John’s vital signs negate systemic sepsis and indicate a localised infection. There are several different classifications of ear infection dependent of the particular area of the ear affected. John has mild pyrexia demonstrating his immunologic response; this is also demonstrated through the purulent discharge he has experienced. Hearing loss or the loss of certain frequencies is a common finding.Infections Affecting the Ear Otitis media – affecting the middle earOtitis externa – affecting the outer earRead the information provided by NHS Direct to gain further information: Pathophysiology Acute otitis media is an infection of the middle ear mucosa resulting in localised inflammation, pain and pyrexia The middle ear connects to the back of the throat via a small channel called the Eustachian tube. Negative pressure or oedema can facilitate direct entry of infectious agents such as viruses or bacteria into the middle ear causing inflammation. Therefore this space can fill with mucus as a consequence of a viral infection such as a cold. The Olfactory System - Smell Smell is referred to as one of the chemical senses; this is because the sense of smell is an evolutionary skill developed to gain insight into the world and its inhabitants. All organic substances are composed of, and emit chemicals which, depending on the particular sensitivity skills of the individual or species can be interpreted or sensed. Function and Form The nose is more than the sensory organ of smell; it plays a vital role in the respiratory system by filtering, warming, and humidifying inhaled air. The lower two thirds of the external nose consists of flexible cartilage, and the upper third is bone. Posteriorly, the internal nose merges with the pharynx and anteriorly with the external nose. The internal and external nose is divided vertically by the nasal septum. In the roof of each nostril is a region called the nasal mucosa. The sinuses serve as resonators for sound production and mucus secretion. The opening between the sinuses and the nasal cavity are lined with mucous membranes that can become inflamed and swollen and can easily become blocked. Common Presentations The most common complaints of the nose are; epistaxis (bleeding nose), blocked nose, runny nose, deformity (usually due to an injury), and loss of smell. Nasal and paranasal disorders present with symptoms such as headache, facial pain, excessive tear production, double vision, bulging eyes, and orbital pain.Mechanical abnormalities, for example a deviated septum or nasal polyp, will usually cause a constant obstruction, whereas the nasal cycle and seasonal allergic rhinitis are usually intermittent, the former alternating between nostrils. Gustatory Sense – Taste The tongue is a large, mobile organ comprising several muscles and covered by a mucous membrane. The base of the tongue is bound laterally by the anterior and posterior tonsillar pillars between which, and on either side, lay the tonsils. The salivary glands secrete saliva into the oral cavity keeping it moist and aiding the first stage of swallowing. As well as an important organ of speech and taste, the tongue has a role in both the mixing of a food bolus and in propelling the bolus towards the pharynx.The Gustatory System Applying Theory to PracticeOne of the functions of the tongue is to facilitate swallowing: Identify some clinical conditions that can affect a patient’s ability to swallowHow can the nutritional demands of these patients be met? ConclusionThe senses facilitate many essential roles to maintain homeostasis and to allow an individual to experience the outside world. These include the ability to perceive and communicate. Through every moment of life an individual will be using at least one of their five senses.  These five senses culminate to allow the brain to adapt to differing environments and to make higher levels of decision-making. A loss of one of more of these functions is life altering and can have a massive impact on an individual and their ability to perform within society.