The gills are frequently involved in several pathological
conditions of diverse aetiology, but lesions should be
differentiated from artefacts and post-mortem changes.
Due to their delicate structure, exposed location, abundant
blood supply and large surface, gills quickly undergo postmortem changes that can make histopathological interpretation difficult (see Fig. 4.31).
2.2
Circulatory System (Cardiovascular
and Secondary Circulation)
2.2.1 The Cardiovascular System
The cardiovascular system is a simple loop with the heart,
gills and systemic circulation in series. The deoxygenated
blood is pumped from the ventricle to the gills where it
leaves as oxygenated blood to be delivered directly to body
organs and tissues.
The heart is located in the pericardial cavity antroventrally to the peritoneal cavity, and is separated from the
latter by the septum transversum (Fig. 2.8). It consists of four
compartments: the sinus venosus, the atrium, the ventricle
Fig. 2.5 Gills and location of interbranchial lymphoid tissue from
Atlantic salmon. Insert medium power
Fig. 2.6 Pseudobranch from an adult sea water farmed Atlantic
salmon
Fig. 2.7 Pseudobranch lamellae of adult Atlantic salmon
Fig. 2.8 Position of normal heart in the pericardial cavity of adult
Atlantic salmon
8
2 Functional Anatomy
conditions of diverse aetiology, but lesions should be
differentiated from artefacts and post-mortem changes.
Due to their delicate structure, exposed location, abundant
blood supply and large surface, gills quickly undergo postmortem changes that can make histopathological interpretation difficult (see Fig. 4.31).
2.2
Circulatory System (Cardiovascular
and Secondary Circulation)
2.2.1 The Cardiovascular System
The cardiovascular system is a simple loop with the heart,
gills and systemic circulation in series. The deoxygenated
blood is pumped from the ventricle to the gills where it
leaves as oxygenated blood to be delivered directly to body
organs and tissues.
The heart is located in the pericardial cavity antroventrally to the peritoneal cavity, and is separated from the
latter by the septum transversum (Fig. 2.8). It consists of four
compartments: the sinus venosus, the atrium, the ventricle
Fig. 2.5 Gills and location of interbranchial lymphoid tissue from
Atlantic salmon. Insert medium power
Fig. 2.6 Pseudobranch from an adult sea water farmed Atlantic
salmon
Fig. 2.7 Pseudobranch lamellae of adult Atlantic salmon
Fig. 2.8 Position of normal heart in the pericardial cavity of adult
Atlantic salmon
8
2 Functional Anatomy