(2007) indicates that due to the more abrasive type of food consumed by animals in captivity they are under increased teeth wear. where D is the short axis or the diameter (D/2 thus equals the internal radius of the left ventricle) and L is the long axis. In a series of legendary studies on the influences of posture and gravity on the cardiovascular systems of giraffes, Goetz and colleagues reported that the high mean Pa is achieved by virtue of an exceptionally large heart (Goetz, 1955; Goetz and Keen, 1957). Giraffe Anatomy. Enter multiple addresses on separate lines or separate them with commas. The Garden Of Eaden Why Do Giraffes Have Long Necks Giraffe In conclusion, our study supports the notion that relative myocardial mass is fairly invariant amongst mammals. The giraffe heart has a relative mass similar to other mammals, but generates twice the blood pressure to overcome the gravitational challenge of perfusing the cerebral circulation. Recently, this has been refuted by several studies demonstrating that the mass of giraffe heart is similar to that of other mammals when expressed relative to body mass. However, several recent and independent investigations, based on much larger sample sizes than the original studies by Goetz, now reveal that giraffes are merely endowed with the same relative cardiac mass as all other mammals, i.e. M.S., M.D. However, the long legs of giraffes appear to reduce energy expenditure required for transport (Pontzer, 2007). 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Big-Hearted Animals . Indeed, the altered Twall/D ratio in the adult giraffe seems to be an example of a beneficial physiological adaptation to a naturally high mean Pa, caused by a high SVR, which is in itself an adaptation to the perfusion requirements of the brain. For that reason, the anatomy of a giraffe is quite amazing. The probe is located in the right atrium (*). Diastolic and systolic septal wall thicknesses were 2.9±0.1 and 3.6±0.1 cm, respectively (P<0.001), and thickening was 23.0±1.3%. It's the best way to learn about our work and how you can get involved! For calculation of chamber volumes, the left ventricle was assumed to have the shape of a prolate hemi-ellipsoid with volume: The diastolic and systolic long-axis lengths were 18.2±0.3 and 15.5±0.3 cm, respectively (P<0.001), resulting in long-axis fractional shortening of 14.9±0.3%. As it is not easy to calculate the total mass of this hypothetical pump, it can only be speculated that the energy cost of such an organ would likewise exceed the average mammalian value by a factor of two or three. A statistical significance level of P<0.05 was used and data are expressed as means±s.e.m. Mean calculated parameters of heart function in the giraffe. A new initiative spearheaded by Directors Sally Lowell, Kate Storey, Alastair Downey and Holly Shiels will provide information, technology and grants to help the community run conferences in a more sustainable way. When the left ventricle is simplified to assume the shape of a thick-walled cylinder, the principle of Laplace states that the mechanical stress exerted on the myocardial wall is proportional to left ventricular pressure (PLV) and its midwall radius (r), whereas it is inversely proportional to wall thickness (Twall): (B) A short-axis view through the giraffe heart at the level of the papillary muscles. It was previously thought that a giraffe had a really big heart, but recent research has revealed that there isn’t room in the body cavity for this. Thus, although the thick ventricular wall resembles the pathophysiological changes during acquired ventricular hypertrophy in response to aortic stenosis or hypertension in humans (Grossman et al., 1975; Hood et al., 1968; Sandler and Dodge, 1963), there is no indication of the secondary myocardial fibrosis in giraffes that inevitably accompanies the acquired left ventricular hypertrophy observed in human disease. The head of a giraffe is small and quite long with a rounded mouth at the end of it. The right ventricle pumps the blood a short distance to the lungs, and the muscle is about 1 cm thick. Long-axis and short-axis shortening, and wall thickening were calculated as the absolute difference between the diastolic and systolic values divided by the diastolic value of the parameter. (1) Anaesthesia was induced by remote injection of etorphine (9 µg kg−1, i.m.) The experimental protocol was approved by the national Danish Animal Experiments Inspectorate (Danish Ministry of Justice), the Animal Ethics Screening Committee at the University of Witwatersrand (Johannesburg) and the Animal Use and Care Committee (University of Pretoria). The phenotypical adaptations to the high arterial pressures in giraffes have been achieved by evolving a low volume, low flow pump that is suitable to maintain cerebral perfusion, but imposes limitations on cardiac chamber size and stroke volume and possibly on maximum sustainable rate of oxygen consumption. Local ethical committee members oversaw the experiments and permission to euthanise the animals was granted by the Gauteng Province of South Africa. Thus, the low VS probably persists during exercise and constrains aerobic performance, and hence limits the maximal aerobic running speed. The giraffe has an extremely high blood pressure (280/180 mm Hg), which is twice that found in humans. In the only other study, Linton et al. Their anatomy and size require a lot from that single heart, which is part of what makes these animals so interesting. The heart of the giraffe would have to be very large in order to pump blood to the brain whilst the giraffe was bent over having a drink. Our echocardiography also revealed a normal mammalian ejection fraction, and hence low ventricular volumes, i.e. A tip transducer catheter (5 French Micro-Tip SPC 350, range −50 to 400 mmHg; Millar Instruments, Houston, TX, USA) was advanced through the carotid artery into the ascending aorta for continuous recording of mean Pa using a Biopack Systems data acquisition software (AcqKnowledge 3.7.2) at 100 Hz. By clicking below to submit this form, you acknowledge that the information you provide will be transferred to MailerLite for processing in accordance with their Privacy Policy and Terms of Service. The solid line indicates the semi-log regression line calculated on the basis of these values, stippled lines indicate the calculated 95% confidence interval. In the literature, we are aware of only two earlier studies of cardiac output, providing data from a total of eight measurements in five giraffe specimens, but several of the values were not corrected for body mass. First of all, the giraffe’s heart is one of the most powerful of that of all the mammals. Corrected stroke volume as a function of total body mass in various extant mammal species. Circumferential and meridional wall stresses were 7.83±4.66 kPa and 7.83±2.28 kPa, respectively. Weighing up to two tons, the giraffe is a colossal animal and unlike any other. Oct 17, 2019 - Explore caitlinbeverly's board "Giraffe Heart" on Pinterest. Diffusion tensor imaging of the left ventricles of a giraffe and a pig. Instead, the giraffe has a relatively small heart and its power comes from a very strong beat as a result of the incredibly thick walls of the left ventricle. Taking the ellipsoid shape of the left ventricle into account, the systolic circumferential and meridional wall stresses (CWS and MWS, respectively) were calculated in kPa as: For example, in order to maintain blood flow to the brain, a giraffe’s heart must generate a blood pressure double that required in humans. The myocardial remodelling clearly seems adaptive to the high mean Pa required for cerebral perfusion, but the resultant decrease in VS obviously imposes a potential limitation to systemic oxygen delivery. First, the skeleton of the giraffe elongates during maturation, more rapidly than that of other mammals. Spots that dissipate heat. The second catheter was advanced into the left ventricle for measurements of left ventricular pressure (PLV). It remains to be determined whether this more than fourfold rise in heart rate is accompanied by altered VS, but the thick ventricular wall probably lowers ventricular compliance and it could be speculated to constrain the ability for the ventricle to alter VS. Thus the echocardiographically derived cardiac output (QE) was 16.1±2.5 l min−1 or 33±12 ml kg−1 min−1. Professor Simon Maddrell’s distinguished career has long been intertwined with the history of The Company of Biologists and JEB. using double-labelled water) and the associated cardiovascular responses to estimate cost of locomotion in free-ranging giraffes. Anaesthesia was maintained by continuous infusion of α-chloralose (KVL Pharmacy, Frederiksberg, Denmark; 30 mg kg−1 h−1 gradually decreasing guided by clinical signs) into the saphenous vein. To investigate the hypothesis that giraffes have a volumetrically small heart with a low intraventricular radius, we determined left ventricular systolic and diastolic dimensions, including wall thicknesses in young anaesthetised giraffes by echocardiography. The colours are therefore merely a visual aid and do not represent any anatomical or physiological properties. Typical corresponding values for a healthy 80 kg human with a heart rate of 70 beats min−1 would be a VED of 150 ml or 1.88 ml kg−1, a VES of 70 ml or 0.88 ml kg−1, a VS of 80 ml or 1 ml kg−1, an ejection fraction of 53.3% and Q of 5.6 l min−1 or 70 ml kg−1 min−1. Please check your email to confirm your subscription. anatomy. A conventional transesophageal echocardiography probe (6T-RS TEE transducer, GE Healthcare, UK) covered with a plastic sheath was inserted into the left jugular vein through the cut-down in the neck and secured with a purse-string suture. In particular, only a handful of studies have concerned the brain of this species since the first description in 1839. Images are not to scale. Peter Agger Nielsen graciously supplied the DTMRI images of the giraffe heart. (A) Giraffe; (B) pig. giraffes have the keenest vision of any African big game animal. Using limb straps to avoid pressure on the thoracic and abdominal regions, the platform was used to hoist the giraffe to an upright position. Cardiac output (Q), in absolute values and expressed relative to Mb, was calculated using the mean heart rate over the time span of the echocardiographic measurements. Echocardiography provided good visualisation of the beating giraffe heart in vivo (see Movie 1 and Fig. Encyclopedia » Anatomy Of Lung Circulation Giraffe En. a pumping chamber that achieves the high mean Pa of giraffes and thus retains the beneficial ratio of radius versus wall thickness reported here while still being able to generate a cardiac output per body mass unit comparable to other mammalian species would have an VED of 1060 ml and a VS of 583 ml, which is approximately twice the measured values. Goetz et al. The rate of oxygen consumption of anaesthetised giraffes resembles that of similar-sized mammals (Langman et al., 1982), and the low VS is in any event unlikely to constrain resting metabolism because an increased arterial–venous oxygen extraction could suffice. We also thank Frederik, Christian and Lisbeth Secher for practical assistance. Organisation of the giraffe cardiac mass. Categories: Encyclopedia. Arterial pressure may exceed 300 mmHg and has historically been attributed to an exceptionally large heart. During all rebreathing procedures, the arterial oxygen saturation exceeded 97% or above, indicating no or minimal pulmonary shunting. Sign in to email alerts with your email address, Department of Clinical Medicine, Aarhus University, 8000, Hans Christian Andersen Children's Hospital, 5000, Department of Cardiovascular and Renal Research, Center for Clinical Research, Vendsyssel Hospital, Aalborg University, Department of Thoracic and Cardiovascular Surgery and Department of Clinical Medicine, Centre for Zoo and Wild Animal Health, Copenhagen Zoo, 1870, Zoophysiology, Department of Biological Sciences, University of the Witwatersrand, Parktown, 2193, Jugular venous pooling during lowering of the head affects blood pressure of the anesthetized giraffe, A modified photo- and magnetoacoustic multigas analyzer applied in gas exchange measurements, Oxygen metabolism and catecholamine secretion during chloralose anesthesia in lambs, Contributions to the anatomy of the giraffe, with an account of the length of the alimentary canal of many other ruminants, Further contributions to the anatomy of the giraffe and the nylghau, Assessment of left ventricular ejection fraction and volumes by real-time, two-dimensional echocardiography. (272 kilograms). In nine anaesthetized giraffes (495±38 kg), we determined in vivo ventricular dimensions using echocardiography along with intraventricular and aortic pressures to calculate left ventricular wall stress. We hypothesized that giraffe hearts have a small intraventricular cavity and a relatively thick ventricular wall, allowing for generation of high arterial pressures at normal left ventricular wall tension. Please log in to add an alert for this article. We do not capture any email address. These studies were part of the second expedition by The Danish Cardiovascular Giraffe Research Programme (DaGIR) in October–November 2010 to Hammanskraal, Gauteng Province, South Africa. A giraffe’s heart has evolved to have thick muscle walls and a small radius giving it great power to overcome this pressure. Unfortunately, too much blood being pumped to its brain at one time would be fatal. We thank all members of the DaGir expedition and the staff at Wildlife Assignment International, South Africa, for assistance with numerous details in relation to handling of giraffes. 0.5–0.6% of body mass (Mb; Brøndum et al., 2009; Mitchell and Skinner, 2009; Østergaard et al., 2013; Perez et al., 2008). The corresponding free wall values were 2.2±0.1 and 3.1±0.1 cm (P<0.001), and thickening was 43.2±3.5%. An overview of calculated variables from echocardiographic data is presented in Table 2. Note how the giraffe heart has both a thicker ventricular wall and a smaller cavity. and guided to a chute where they were blindfolded. This method has obviously not been validated because our study is the first to report the use of echocardiography on the giraffe heart and no gold standard for measurements in this species exists. It is also noteworthy that newborn giraffes have a myocardial wall thickness relative to ventricular diameter that is similar to other mammals, such that the ventricular wall thickening seems to arise as mean Pa increases with neck length (Mitchell and Skinner, 2009). Research reveals that giraffes have a supercharged and a small heart that is different than other similar animals. Puzzling long neck. Though a giraffe's heart is huge — it's 0.6 meters (2 feet) long and weighs about 11 kilograms (25 pounds) — the great height of a giraffe still makes it hard for the heart to pump blood to the brain. Orientation is equivalent to four-chamber view of human heart. The low cardiac output of giraffes alleviates the influence of the high mean Pa on the workload of the heart. To visualise the three-dimensional architecture of the left ventricular myocardium in terms of cardiomyocyte pathways we performed diffusion tensor imaging (DTI) with MRI on one giraffe heart with a Philips 1.5 T Achieva system. Essentially, the DTI technique allows for visualisation of the orientation of the cardiomyocytes. (4) There does not appear to be any significant difference in myocardial architecture of the giraffe compared with other mammals. The thickness of the muscle wall is related almost directly to the length of the neck. The giraffe heart generates twice the pressure of simi-lar-sized mammals under normal physiological condi-tions (Goetz and Budtz-Olsen O., 1955; Van Citters et al., 1966; Br ndum et al., 2009) with a relative ven-tricular mass no different from other mammals, that is, 0.5% of body mass (Fig. Programme Updates. where ΔPLV is the change in left ventricular pressure (approximated as the systolic minus the diastolic pressure). The low VS is corroborated by the independent measures of low CO using the inert gas-rebreathing technique, and it is clear therefore that the normalisation of ventricular wall stress by the low radius ventricle constrains oxygen delivery by the cardiovascular system. To minimise the influence of the induction agents on the cardiovascular system, the effect of the etorphine was reversed with naltrexone and measurements were obtained after the effects of medetomidine and ketamine were expected to have subsided (more than 90 min after administration; Brøndum et al., 2009). ), the giraffes were placed in right lateral recumbency on a custom-made movable platform. Proceeds from every sale help fund our conservation work in Africa. ), which rendered the giraffes recumbent within minutes. End-diastolic and end-systolic volumes were 521±61 ml and 228±42 ml, respectively, yielding an ejection fraction of 56±4% and a stroke volume of 0.59 ml kg−1. The Human Neck Anatomy of the human Spine. the so-called helical angle distribution (the inclination of the cardiomyocyte tracks relative to the equatorial plane of the left ventricle), as well as the pattern of myocardial pathways, did not reveal any obvious differences compared with other mammals (Scollan et al., 1998; Smerup et al., 2009). Thus, our study provides strong evidence for a considerably lower cardiac output in giraffes than in other similar-sized mammals. The rebreathing technique provides a reliable measure of effective pulmonary blood flow (Gabrielsen et al., 2002), but could underestimate systemic cardiac output in the presence of pulmonary shunts. In fact, the calculated wall stress of the left ventricle in the giraffes is virtually identical to that reported for other mammals (Seymour and Blaylock, 2000). ... Their heart beats around 150 times/minute. The thickness of the muscle wall is related almost directly to the length of the neck. 2) and hence allowed us to determine cardiac dimensions during the entirety of the cardiac cycle. also giraffes brain is half the size of a humans brain, but has twice as much blood pressure of a humans. (1,360 kg). Data are from Seymour and Blaylock, 2000. The cardiovascular measurements completed in the present study would be virtually impossible to achieve in conscious animals where the necessary restraint and handling stress would be ethically unacceptable and cause considerable disturbance to haemodynamic variables. Black, Pa; red, PLV; blue, PRV. Giraffes have many special features like it's horn structure that is called ossicones which cartilage fused to the skull. An astounding side effect of the long neck is that the giraffe needs a powerful heart to pump blood up to the head and brain. (2007) studied the tooth wear in a captive giraffes. RV, right ventricle; IVS, intraventricular septum; LV, left ventricle; PM, papillary muscle. and T.W. The left ventricle has to pump the blood all the way up to the head against the hydrostatic pressure of the blood already in the long vertical artery. Our work also confirms that the systemic vascular resistance (SVR) of giraffes is considerably higher than that of other similar-sized mammals. Accordingly, only a very few articles discussing encephalization mentioned the giraffe or used it in their calculations. (5) (3) Since we also confirmed the conspicuously high mean Pa and the associated high intraventricular pressures in the giraffe, our findings support the hypothesis that the combination of thick left ventricular wall and a low radius of the left ventricular cavity allow for a normal mammalian myocardial wall stress in the giraffe heart.
2020 giraffe heart anatomy