A16 & A17 Thorax Flashcards
Describe the boundaries & openings of the thoracic cavity
Dorsal: thoracic vertebrae
Ventral: sternum
Lateral: ribs, costal cartilage, intercostal mm.
Caudal: diaphragm
Cranial: thoracic inlet
Thoracic inlet is a hiatus between 1st ribs, sternum & spinal column (T1)
Allows structures such as oesophagus, trachea, common carotid arteries, jugular veins & nerves to pass through
What is the difference between visceral pleura & parietal pleura
Pleura is a serous membrane that forms a 2-layer pleural sac
Visceral pleura - covers organs/blood vessels
Parietal pleura - covers body wall
Describe the distribution of costal, diaphragmatic, mediastinal & pulmonary pleura
Costal pleura - covers ribs
Diaphragmatic- covers the diaphragm
Mediastinal - covers the boundary of the mediastinum
Pulmonary - covers the lungs
Identify the organs contained within the thorax
- Heart
- lungs
- oesophagus
- diaphragm
- thymus
How is mediastinum formed & what organs/structures are contained within
The space between the left & right pleural cavities is called the mediastinum.
It contains various organs & tissues such as:
- thymus
- heart
- major blood vessels
- oesophagus
- nerves
- lymph vessels
- trachea
Describe the arrangement of the pericardium & pericardial cavity
Pericardium is a fibro-serous membrane around the heart with 2 layers & fluid in the pericardial cavity. The visceral serous pericardium is the layer closest to the heart which reflects to become parietal pericardium - this has two fused parts, inner smooth serous part & an outer fibrous part
Describe the main thoracic arteries
Aorta
↓
Brachiocephalic trunk
→ right subclavian a. → vertebral a, costa cervical a, superficial cervical a, maxillary a, internal thoracic a
→ right common carotid a.
→ left common carotid a.
↓
Left subclavian a.
Describe the main thoracic veins
Caudal vena cava
Azygous vein
Cranial vena cava
↓
R. External jugular v → R. Internal jugular v
↓
L. Brachiocephalic v
→ L. Subclavian v.
→ L. Internal jugular v
Describe the course of the main nerves
Vagosympathetic trunk divides at middle cervical ganglion
Vagus nerve continues caudally, gives off recurrent laryngeal nerve, then splits into dorsal & ventral branches
Sympathetic trunk continues dorsally then causally at thoracic vertebrae
Phrenic nerves arise from spinal nerves 5,6 & 7 & innovate the diaphragm
Describe the course of the thoracic duct
Thoracic duct is a collecting channel for lymph from lymphatic capillaries & ducts & returns the lymph to the venous system.
Runs carnally on the right dorsal border of the aorta
Crosses to left side at level of T5
Continues carnally in mediastinum of the left lateral surface of oesophagus to enter the left brachiocephalic V.
Describe the position of the mediastinal, tracheabronchial & sternal lymph nodes
Mediastinal lymph nodes - cranial mediastinum
Tracheabronchial lymph nodes - trachea
Eternal lymph nodes - cranial sternum (manubrium)
Describe the position of the thymus
Thymus is a bi-lobed muscle in the cranial mediastinum in young animals, and is large until it regresses to become adipose tissue at 4 months.
Important for immune system as it produces & selects t-lymphocytes
Describe the diaphragm & its blood & nerve supply
- The diaphragm is mostly skeletal muscle innovated by phrenic nerves
- has an outer muscular part & central tendons part
- acts as a partition between thoracic & abdominal cavities
- covered in diaphragmatic pleura
- sternal attachment to xiphoid cartilage
- costal attachment to medial surfaces of ribs 8-13
- lumbar attachment at ventral bodies of 3rd & 4th lumbar vertebrae
3 foramina
- aortic hiatus (aorta, azygous v, thoracic duct, sympathetic trunk)
- oesophagus hiatus coesophagus, vagal nerves)
- Caval foreman (caudal vena cava)
Describe the topography of the lungs
Left lung
- cranial (cranial & caudal part)
- caudal
Right lung
- cranial
- middle
- caudal
- accessory lobe
Trachea → right principal bronchus → lobar bronchi of right lung
↓
Left principle bronchus
↓
Lobar bronchi of Left lung
Describe the body wall muscles responsible for breathing movements & explain their actions
Muscles involved in respiration include:
- diaphragm
- scalenus
- serratus dorsalis cranialis
- external intercostal m. & internal intercostal m.
During inspiration the ribs move down, out and forwards increasing the thoracic cavity. Diaphragm flattens causing longitudinal diameter to increase, the serratus dorsalis cranialis m. lifts the ribs
During expiration the muscles are passive due to elastic recoil of lungs. In exercise, the internal intercostal m, serratus dorsalis caudalis & abdominal m. are involved.
