Ross & Wilson Anatomy and Physiology in Health and Illness (35 page)

The two main forms of haemophilia differ only in the clotting factor involved; the clinical picture in both is identical.

•
Haemophilia A. In this disease, factor VIII is abnormal and is less biologically active.

•
Haemophilia B (Christmas disease). This is less common and factor IX is deficient, resulting in deficiency of thromboplastin (clotting factor III).

von Willebrand’s disease

In this disease, a deficiency in the von Willebrand factor causes low levels of factor VIII. As the inheritance is not sex linked, haemorrhages due to impaired clotting occur equally in males and females.

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.

CHAPTER 5

The cardiovascular system

Blood vessels
74

Control of blood vessel diameter
76

Capillary exchange
77

Heart
78

Position
78

Structure
79

Flow of blood through the heart
81

Blood supply to the heart (the coronary circulation)
82

Conducting system of the heart
83

The cardiac cycle
84

Cardiac output
85

Blood pressure
87

Factors determining blood pressure
87

Control of blood pressure (BP)
88

Pulse
90

Circulation of the blood
91

Pulmonary circulation
91

Systemic or general circulation
94

Aorta
94

Summary of the main blood vessels
106

Fetal circulation
108

Features of the fetal circulation
108

Changes at birth
110

Shock
111

Thrombosis and embolism
112

Blood vessel pathology
113

Atheroma
113

Arteriosclerosis
115

Aneurysms
115

Venous thrombosis
116

Varicose veins
116

Tumours of blood and lymph vessels
117

Oedema
117

Ascites and effusions
118

Diseases of the heart
119

Heart (cardiac) failure
119

Disorders of heart valves
120

Ischaemic heart disease
120

Rheumatic heart disease
121

Infective endocarditis
121

Cardiac arrhythmias
122

Congenital abnormalities
123

Disorders of blood pressure
124

Hypertension
124

Hypotension
126

ANIMATIONS

5.1
Blood vessels
74

5.2
Location of the heart
78

5.3
Chambers of the heart
80

5.4
Heart valves and sounds
81

5.5
Left ventricular valves
82

5.6
Coronary circulation
82

5.7
Conduction of heart impulses
83

5.8
Events represented by the ECG
85

5.9
Pulse points
90

5.10
Pulmonary circulation
91

5.11
Hepatic portal circulation
102

5.12
Fetal circulation
108

5.13
The effects of atheroma on blood flow
114

5.14
Disorders of the heart valves
120

The cardiovascular (cardio – heart, vascular – blood vessels) system is divided for descriptive purposes into two main parts:

•
the
heart
, whose pumping action ensures constant circulation of the blood

•
the
blood vessels,
which form a lengthy network through which the blood flows.

The
lymphatic system
is closely connected, both structurally and functionally, with the cardiovascular system and is discussed in
Chapter 6
.

The heart pumps blood into two anatomically separate systems of blood vessels (
Fig. 5.1
):

•
the pulmonary circulation

•
the systemic circulation.

Figure 5.1 
The relationship between the pulmonary and the systemic circulations.

The right side of the heart pumps blood to the lungs (the pulmonary circulation) where gas exchange occurs, i.e. the blood collects oxygen from the airsacs and excess carbon dioxide diffuses into the airsacs for exhalation. The left side of the heart pumps blood into the systemic circulation, which supplies the rest of the body. Here, tissue wastes are passed into the blood for excretion, and body cells extract nutrients and O
₂
.

The circulatory system ensures a continuous flow of blood to all body cells, and its function is subject to continual physiological adjustments to maintain an adequate blood supply. Should the supply of oxygen and nutrients to body cells become inadequate, tissue damage occurs and cell death may follow.

Disease of the cardiovascular system is likely to have significant consequences, not only for the heart and blood vessels, but also for other body systems, which is discussed from
page 111
.

Blood vessels

Learning outcomes

After studying this section, you should be able to:

describe the structures and functions of arteries, veins and capillaries