Respiratory system

Respiratory system
The respiratory system consists of nose & trachea & bronchial tree and the two lungs.
Trachea:
Def.: membranous tube of many cartilaginous rings.
Extends from larynx to the lungs where it bifurcates into two principle bronchus.
Divided into thoracic & cervical parts
Section of the cervical part:
1-longus coli muscle
2-cervical vertebrae
3-sternothyroid muscle
4-common carotid artery
5-vagus nerve
6-recurrent nerve
7-esophagus
8-omohyoid muscle
9-jugular vein

Section of the thoracic part:
1-brachiocephalic trunk (from the aortic arch)
2-aorta
3-caudal vena cava
4-cranial vena cava
5-longus coli muscle
6-vertebral column
7-trachea
8-esophagus

*The longus coli muscle extended along the thoracic part until its bifurcation (it stops)
*The trachea bifurcates at the base of the heart

The comparative features of trachea among animals:
1-num. of tracheal rings:
· Camel: 90
· Horse: 60
· Ox: 50
· Sheep & goat: from 40: 50
· Dog: 40
· Pig: 30

2-shape of tracheal ring:
· Camel & dog & pig: circular
· Horse: oval or ovoid
· Ox & sheep: oval
· Goat: U shape

3-the end of the rings:
The ends of the ring connected with tracheal muscle that is retro mucosal in all animals except dog is outside the ring
· Camel & sheep & pig: rings overlapped to the right
· Horse: overlapped to the left
· Dog & goat: does not overlapped at all

The bronchial tree:
· Def.: framework of bronchial divisions in the form of branches of tree
· The divisions: trachea give RT & LT bronchus. Each one gives lobar bronchi then num. of segmental bronchioles then num. of subsegmental bronchioles then num. of small bronchioles (less than 1 mm in diameter ) then ends with terminal bronchioles & respiratory bronchioles


The thoracic cavity:
*Thoracic cage

Def.: cage of bone in the form of lateral flattened cone shape where the apex is cranially located & the base caudally

Consists of:
1-cranial inlet: bounded by:
a- dorsally: first thoracic vertebrae
b- ventrally: first sternebra
c- laterally: first pair of the ribs

2-caudal outlet: bounded by:

a- dorsally: last thoracic vertebrae
b- ventrally: xiphoid cartilage
c- laterally: costal attachment of diaphragm

*Structures passes through thoracic inlet:
1-Trachea
2-Esophagus
3-Nerves of thorax & limbs & head & neck
4-Cranial mediastinal lymphocentre
Blood supply of head &neck & forelimb & lateral thoracic wall

*Openings of thoracic outlet:
1-Aortic hiatus
2-Esophageal hiatus
3-Caval hiatus

The pleura:
Def.: thin slippery serous membrane lines the thoracic cavity arranged in the form of two pleural sacs

Layers of pleural sacs:
1-parietal layer: consists of costal & diaphragmatic & cervical parts
2-pulmonary or visceral layer: located allover the lung except at the root of the lung
3-mediastinal part: double layers covers viscera in mediastinal space called pericardial pleura when covers the pericardium