LASTA

• Horse lung fields: Basal border begins at the 6th rib (about 2 fingers above the olecranon) then runs along to the 10th intercostal space then to the level of the tuber ischii at the 14th intercostal space, ending at the 18th rib (tuber coxae level)
• the spleen filters the blood, removing aging erythrocytes and antigens. Also has a role in haematopoiesis in the foetus. It also acts as an erythrocyte reservoir - horses can contract their spleen during exercise under sympathetic control to increase RBC concentration
• the spleen sits on the left hand side. In the horse it sits between the tenth rib and the 18th rib
• the mediastinum is the space between the R and L pleural cavities between the two mediastinal pleura
• The pleural cavity is the space between the parietal costal and diaphragmatic and mediastinal pleura and the visceral pulmonary pleura covering the lungs
• the pericardial cavity is the space between the parietal and visceral pericardium which allows the heart to beat in a lubricated cavity
• Structures present within the mediastinum:

  • Thymus
  • trachea
  • oesophagus
  • cranial and caudal vena cava
  • azygous vein and associated veins
  • aorta and associated arteries
  • thoracic duct
  • nerves and associated ganglia
  • lymph nodes
• List the layers traversed to reach the myocardium of the left ventricle from the pleural cavity

  mediastinal pleura, fibrous pericardium, parietal pericardium, visceral pericardium
• How is the gross topography of the heart different between the horse and the dog?

  Horse heart sits in a more vertical position and is concave on the caudal border
• How is the branching pattern of the aorta different between the horse and the dog?

  In the horse the left subclavian artery branches off the brachiocephalic trunk as well as the right and right and left common carotid arteries. In the dog the left subclavian artery branches directly off the aorta
• Normal palpation of the equine rectum should present:

  Left dorsal quadrant: caudal edge of spleen, nephrosplenic ligament and caudal pole of left kidney

  Dorsal: aorta, mesenteric root

  Right dorsal quadrant: base of caecum, ventral and medial ceacal bands

  Ventral: bladder, uterus

  Left ventral quadrant: pelvic flexure,
• why does the anatomy of the equine lungs make it difficult for them to lie down for extended periods?

  Equine lungs are thick dorsally but very thin ventrally so the guts can impinge on the lungs when lying down, making it difficult to breathe
• pericardiocentesis is taken at the 5th intercostal space, between the level of the point of the shoulder and the point of the elbow. alternatively 6 or 7 lower
• abdominocentesis is taken through the linea alba at the most dependent point of the abdomen (hand's breadth from the xiphisternum)
• a liver biopsy is taken through the right hand side at the 13th intercostal space, within a triangle drawn from the point of the shoulder, point of the elbow and tuber coxae
• Thoracocentesis is taken at the 7th or 8th intercostal space on the left or 6th or 7th on the right - 10cm above the point of the elbow
• the infraorbital foramen lies under the tip of the middle finger when the hand is placed at the rostral end of the facial crest. It is covered by the levator labii superiosus muscle. The infraorbital nerve is sensory to incisors and premolars
• the mental foramen can be felt just ventral to the commissures of the lip along the bone of the rostral mandible. the tendon of the depressor labii inferioris m lies over it. The mental nerve passes through and provides sensory innervation to the rostral mandible, canines, incisors and lower lip
• the supraorbital foramen can be felt as a dimple in the root of the zygomatic process of the frontal bone. The supraorbital nerve emerges with the supraorbital artery. Sensory supply to upper eyelid
• the auriculopalpebral nerve crosses the caudal end of the zygomatic arch. Nerve block can be placed between the caudal end of the arch and the base of the ear to block the motor control to the upper eyelid
• the auditory tubes join the middle ear to the nasopharynx. They equilibrate the pressure in the middle ear. Communicate through slit-like openings in the nasopharynx. Made up of medial and lateral laminae joined dorsally with the ventral mucosal diverticulum (guttural pouches)
• the guttural pouches are divided by the stylohyoid bones. The medial compartment is larger than lateral.
• the guttural pouches are lined with respiratory epithelium
• the rectus capitis muscles divide the left and right pouches mediodorsally . medioventrally mucus membranes form a septum
• medial guttural pouch contains glossopharyngeal, vagus, accessory and hypoglossal nerves (IX, X, XI and XII). The medial compartment fold contains the internal carotid a, cervical sympathetic nerve and cranial cervical ganglion
• lateral guttural pouch contains the facial nerve (VII), the external carotid artery , maxillary artery and the maxillary vein
• the vagus nerve has a chronotropic effect on the heart- slows. The preganglionic neurotransmitter is ACh on nicotinic receptors. The postganglionic neurotransmitter is ACh on M2 muscarinic receptors
• the sympathetic trunk has a chronotropic effect on the heart- speeds it and increases strength of contraction. The preganglionic neurotransmitter is ACh on nicotinic receptors. The postganglionic receptor is noradrenaline acting on B1 adrenoceptors.