Thorax- respiration Flashcards
Diaphragmatic hernia
Liver (or other organ) herniated due to a torn diaphragm. Occupying the space where the lungs normally are.
General formation of the pleural and pericardial cavities
- Coelom is divided into right and left by dorsal and ventral mesocardium (future mediastinum)
- Pleuro-pericardial folds (mesoderm) separate lungs (pleural cavity dorsally) and the heart (pericardial cavity ventrally)
- The left and right pleural cavities will extend around pericardial sac
Pleuro-pericardial folds
- Mesoderm
- Separate the lungs (pleural cavity dorsally) and the heart (pericardial cavity ventrally)
Serous membranes
- Serosal fluid surrounds body cavities allowing them to slide around/move freely with body movements
- Flat mesothelial cells with underlying connective tissue
- Lungs= pleural serosal membrane (pleura)
- Heart= Serous pericardium
Muscles of the thoracic wall
- Scalenus
- Serratus ventralis (extrinsic)
- Serratus dorsalis
- Intercostals
- Rectus thoracis
- Transversus thoracis (inside thoracic cage)
- Diaphragm
Muscles of the thoracic wall purpose
Primarily for respiration
- Inspiratory- enlarging the thoracic cavity
- Expiratory- diminish cavity and expel air
Intercostal muscles
Arranged in 3 layers. Function to draw ribs together during respiration
External intercostal muscles- outermost, fibers run caudoventrally from rib to rib. Don’t meet the sternum. They fill the space until the costochondral junctions
Internal intercostal muscles- deeper, fibers run cranio-ventrally. Don’t occupy the most dorsal parts of the space, but they do meet the margin of the sternum.
Subcostal layer- weak, and inconsistent layer
Transversus thoracis
- Triangular sheet that arises from and covers the dorsal surface of the sternum
- Inserts on the costochondral junctions
Rectus thoracis
Placed over the lower ends of the first four ribs
Serratus dorsalis
- Lies over the dorsal parts of the ribs
- Origin from fascia of back and inserts on the ribs
- Plays a role in lifting ribs for inspiration (cranial part) and drawing the last 3 ribs caudally in expiration (caudal part)
Serratus ventralis
- Large, fan shaped muscle
- Origin on the neck, insertion on serrated face of scapula
Scalenus
- Attaches on first rib
- Stabilizes ribs during inspiration
Openings of the diaphragm
- Aortic hiatus
- Esophageal hiatus
- Caval foreman- caudal vena cava
What nerves supply the thoracic wall muscles?
- Diaphragm- supplied by phrenic nerves (somatic)
- Other muscles- supplied by intercostal nerves
Systemic circulation
- Left ventricle feeds into the aorta.
- The aorta branches into the dorsal intercostals, paired (left or right) subclavian, and the brachiocephalic trunk
- Subclavian artery supplies blood to the forelimb and to structures of the neck and cervicothoracic junction.
Branches:
- Axillary artery- To get to limb, it winds around the cranial border of the first rib and enters through the axilla, therefore becoming the axillary artery
- Vertebral artery- Also branches to become the vertebral artery which dives between the scalenus and longus colli muscles passing through the transverse foramina of the 6th to 1st vertebra
- Costo-cervical trunk- supplies the first few dorsal intercostal arteries and the deep cervical artery which ascends the neck
- Internal thoracic artery- curves ventrally within the mediastinum to pass between the transversus thoracic and the sternum. This one continues below the diaphragm into the abdomen
- Superficial cervical artery- the arises near the origin of the internal thoracic. Supplies the muscles of the ventral part of neck, cranial part of shoulder, and the upper arm
- Brachiocephalic trunk branches into the carotids (supply blood to the head) and the right subclavian (same as left on other side of body)
Brachiocephalic trunk
- In species other than the dog and pig, the brachiocephalic trunk is composed of both the left and right subclavian and the carotids.
- In the dog and pig, the left subclavian is separate
Nerves
- Nerve of each intercostal space divide into dorsal and ventral branches when emerging from the intervertebral foramen
– Dorsal branches enter the epaxial muscles, ventral branches descend into the intercostal space along the caudal border of each rib
Ventral branches
Become intercostal nerves which branch into the lateral cutaneous branch and the ventral cutaneous branch
- Lateral: Emerge at regular intervals between skin and supply cutaneous muscle, subcutaneous tissue, and skin
- Ventral: Emerge from deep pectoral after penetrating the ventral ends of intercostal spaces. They are the terminal branches of the intercostal nerves
Dorsal branches
- Enter epaxial muscles
- Medial and lateral branches