The structural organization of the carotid arterial system of the giraffe (Giraffa camelopardalis)
Carotid arteries in the giraffe were removed and their structural organization studied with light microscopy. It has been shown that the carotid artery has a largely muscular structure in the adult except for the carotid baroreceptor area located at the carotid‐occipital junction. The fetus carotid has an elastic structure in its caudal portion and a […]
Gravitational haemodynamics and oedema prevention in the giraffe
Because it is so tall, the giraffe, Giraffa camelopardalis, provides an important animal model for investigating adaptive mechanisms to orthostatic (gravitational) pressure changes. Previous physiological studies of the giraffe have concentrated on arterial blood pressures in the heart and neck. Briefly, these investigations revealed that arterial pressure near the giraffe heart is about twice that […]
Note on sleep in captive giraffes (Giraffa camelopardalis reticulata)
The relatively small amount of time spent sleeping by giraffes, can be attributed most directly to the need for constant rumination. This is consonant with the more general ecological notion that sleep patterns in prey species are usually characterized by brief, intermittent periods of sleep.
Blood pressure and flow rate in the giraffe jugular vein
Experimental measurements in the jugular veins of upright giraffes have shown that the internal pressure is somewhat above atmospheric and increases with height above the heart. A simple model of steady viscous flow in an inverted U-tube shows that these observations are inconsistent with a model in which the blood vessels in the head and […]
Urinary steroid evaluations to monitor ovarian function in exotic ungulates: II. Comparison between the giraffe (giraffa camelopardalis) and the okapi (okapia johnstoni)
Ovarian activity in the female giraffe was evaluated during the nonfertile ovarian cycle and during the terminal stages of gestation. Progesterone metabolites, in the form of pregnanediol‐3‐glucuronide (PdG), were measured in daily random urine samples collected from four adult parous giraffes. The follicular phase averaged 4.0 ± 0.1 days in length (N = 12; range […]
Physiological cross-sectional area of the masticatory muscles in the giraffe (Giraffa camelopardalis)
Numerous studies have investigated how the skeletal morphology is related to feeding behaviour (Christiansen and Adolfssen 2005; Wroe et al. 2005; Christiansen and Wroe 2007; Ellis et al. 2009; Koyabu and Endo 2009; Koyabu et al. 2009; Koyabu and Endo 2010), although remarkably few studies have focused on the architecture of masticatory muscles from which […]
Observations on the giraffe central nervous system related to the corticospinal tract, motor cortex and spinal cord: what difference does a long neck make?
The mammalian corticospinal tract is known to contain axons that travel from the cerebral cortex to various levels of the spinal cord and its main function is thought to be the mediation of voluntary movement. The current study describes neuroanatomy related to the corticospinal tract of the giraffe. This animal presents a specific morphology that […]
Fecal steroid analysis of female giraffe (Giraffa camelopardalis) reproductive condition and the impact of endocrine status on daily time budgets
Gestation and lactation can impose substantial energetic costs on female mammals. We developed a non-invasive means to determine reproductive condition in female giraffe using fecal steroid analysis. Giraffe may be especially challenged during their reproductive cycle because of two characteristics: they are impregnated while lactating and they do not breed seasonally. We studied the social […]
Cerebral perfusion pressure in Giraffe: Modelling the effects of head-raising and – lowering
Loss of consciousness caused by positional changes of the head results from reduced cerebral blood flow (CBF). CBF is related to cerebral perfusion pressure (CPP). CPP is the difference between mean arterial pressure (MAP) at the head and intracranial pressure (ICP). The positional change of the giraffe head between ground level and standing upright is […]
Carotid Haemodynamics in the Giraffe
In a research letter to this journal on the physiology of the giraffe, McCalden et al. suggested that cranial blood flow in the giraffe is regulated by an autoregulatory response of the cranial vasculature. Their conclusion was based on two points: 1) that carotid flow remains constant over a wide range of carotid pressures, and […]