Johnny Bravo’s square jaw vs Popeye’s round jaw: A scientific explanation

From left to right, popular cartoon characters Ferb, Phineas, Popeye, and Johnny Bravo.

Do you ever scratch your head and roll your eyes at the ridiculous shapes of cartoon characters? While it can’t be confirmed that Phineas and Ferb have legitimate jaw bones, there may be a scientific explanation to Popeye’s rounded jaw to Johnny Bravo’s square jaw.

A recent study published online in Scientific Reports on April 16, 2018, validated a significant association between mandibular shape and jaw muscle cross-sectional size. In other words, researchers found that thicker jaw muscles produced broader, bigger, and more rectangular jaw bones.

Previous studies have shown that craniofacial skeletal form, or the structure of the bones of the face and jaw, is influenced by mechanical loading. Just as your leg bones get stronger from running, and arm bones get stronger from lifting weights, jaw bones get stronger from chewing. The specific shape of the mandibular bone is also determined by the forces applied to it throughout development. So, you might get your dad’s square jaw through genetics, but you also have a square jaw because of the foods you eat regularly.

Jaw muscles
The temporalis muscle and master muscle of the skull. Credit: Sella-Tunis et al. Labels added.

Scientists at Carmel Research Center in Israel measured jaw shapes and jaw muscles in 382 adult patients by utilizing CT scans. These scans allow for visualization of both bone and muscle, and they specifically looked at (1) the temporalis muscle, which is a large, round muscle that reaches from the side of the skull to the side of the face, and (2) the masseter muscle, which stretches from the lower jaw to the upper jaw.

Jaw bone
Comparison of jaw bone size and shape. Credit: Sella-Tunis et al. Labels added.

Independent of gender and accounting for relative size of individuals, researchers found that larger jaw muscles resulted in a wider ramus, a bigger coronoid projection, a more rectangular base, and a more rounded basal arch. Alternatively, smaller muscles produced a skinnier ramus, a smaller coronoid projection, a narrower and angled base, and a more triangular basal arch (see picture above).

This research can be used in anthropology contexts. Researchers suspect that  hunter-gatherer populations had harder diets, comprised of nuts and meat, which generate larger muscles and produced a stronger jaw line, while agricultural groups that ate more vegetation had skulls that resembled the jaws with smaller muscles. According to this data, it is plausible that Popeye’s spinach diet led to the growth of his softer, rounder jaw, and I would guess that Johnny Bravo is a fan of tougher foods.


Sella-Tunis, T., Pokhojaev, A., Sarig, R., O’Higgins, P., & May, H. 2018. Human mandibular shape is associated with masticatory muscle force. Scientific Reports 8. [doi: 10.1038/s41598-018-24293-3].



Radiation in Clinical Care

Biomedical Imaging

Medical Intensive care unit (MICU) patients are exposed to radiation higher than annual US Federal occupational standard limits within a short period of time during radioscopic studies. Research conducted between January and December 2013 by scientists at the Cleveland Clinical Foundation discovered this to be true among 3% of the total 4155 patients involved in the study. 

The millisievert (mSv) is a measure of the organic effect of ionizing radiation and is known as the effective dose (ED). Statistical tests conducted on the data obtained in the study showed that 36% of the patients were exposed to radiation higher than the natural background radiation (~3 mSv). Values just 3-5 times higher have been suspected to cause carcinogenesis, although the debate is still ongoing.

Radiation is used in numerous reliable diagnostic procedures in the MICU. Although this has been overshadowing the potential risk of cancers, recently, more medical literatures are exploring its adverse effects. The study also showed an increase in cumulative ED for patients with a higher length of stay at the MICU. Among the radiation based Imaging systems used in healthcare, CT and IR caused the highest amount of radiation burden. However, diagnosis of sepsis, COPD, cirrhosis and Gastrointestinal bleeding were seen to affect cumulative ED. 

radiation burden data distribution
Figure 1 shows the distribution of data obtained by Krishnan et al for radiation burden

Ionizing radiation can lead to cancers by damaging our DNA or RNA, and cause genetic abnormalities. This is especially true for kids and young adults who have a high rate of cellular division and a longer lifespan to express the effects of radiation. Krishnan et al report that despite their adoption of the ALARA (‘as low as reasonably achievable’) principle of radiation safety, patients were exposed to substantial amounts of radiation during diagnosis. Therefore, they suggest methods for assessing the risk vs benefit of radiation therapy.

“Proactive monitoring of CED with real time display in electronic medical resorts will assist physicians in deciding the risk-benefit ratio.”

The study was limited as it was conducted among MICU patients from a single academic medical center. The estimate of ED from previous papers and the limited medical records from which data was obtained could have caused an undervaluation of the cumulative ED. Another shortcoming was the disregard for patient basic characteristics like age and sex. Nevertheless, the results denote a need to conduct more research to weigh the pros and cons of radiation in medicine and its effects on overall patient health.

This makes me wonder, are we so highly dependent on radioscopic resources that we fail to consider the harm it might be doing us? At this day and age of technological advancement, there should be active endeavors to explore the benefits and possible disadvantages of radiation in the medical industry and ways to alleviate them.

Reference: Krishnan S, Moghekar A, Duggal A, Yella J, Narechania S, Ramachandran V, Mehta A, Adhi F, Vijayan AKC, Han X, Dong F, Martin C III, Guzman J, Radiation Exposure in the Medical Intensive Care Unit- Predictors and Characteristics, CHEST (2018), doi: 10. 1016/ j.chest.2018/01/019.

Link to article

Canadian Light Source Research Office