To examine the hypothesis that the glans penis acts protectively, absorbing forces, during coitus. Five potent patients (mean age 46.8±9.7 y), who had indication for surgical excision of the glans for penile carcinoma were included in the present study. Intraoperatively, intracavernosal pressure (ICP) was adjusted by saline infusion and maintained by a pressure feedback infusion pump to a pressure value of 70 mmHg. Using a dynamometer, an external compressive force of 0.5 kg was applied at the glans penis and the changes in ICP were monitored. Measurements were repeated after surgical excision of the glans. Significant ICP changes were noticed in all patients after excision of the glans. Mean preoperative ICP was 161±11.5 mmHg, while after glansectomy it reached 206.6±13 mmHg. ΔICP was 45.8±10.57 mmHg. Two of the patients' partners reported pain during intercourse postoperatively, possibly due to the impact of the force applied by the rigid corpora cavernosa on the anterior vaginal wall without any absorption by the glans. The glans penis restricts the increase in ICP during sexual intercourse, playing a protective role for both the corpora cavernosa and the female genitalia.
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The mechanical behaviour of the examined structure in this paper (penis with and without the glans) can be initially modelled as shown in Figure 2.
Both cases (I, II) can be treated as columns subjected to an axial compressive static load, which in the specific application had a value of 0.5 kp.
The observation was made such that the pressures needed to render the two structures (I, II) capable to withstand the load P without buckling are: σI=206±13 mmHg and σII=161±11.5 mmHg, respectively.
This means that stresses σcrI=−σI and σcrII=−σII are developed in each section of the structures, respectively.
Considering buckling of a column, having Young's modulus E, length L, moment of inertia I and section A, and loaded with a compressive axial load, the critical load of components I, II can be expressed according to the following equations:19,20
where V(x) is the deflection function.
From equations (1) and (3) we get
Splitting the integral on the left side of the inequality leads to
Considering that A2=A1, I2=I1, E2=E1, inequality (5) can be reduced to
The function V(x) is of the type: V(x)=C, sin (πx/L), where C=constant.
According to Abramowitz-Stegun21 (relationship 4.3.139, p. 78), for α=0, n=2, b=π/L1, and z=x:
From equations (6) and (7) we can write
Similarly, we can write
Applying relationship (4.3.138) from Abramowitz and Stegun:21
From equations (8) and (9) we get
For a circular section
From equations (10) and (11)
Inequality (12) is valid because d1, d3>0, d1<d3 → d12<d32 and E1<E3, given that the construction with glans is the initial penis construction, reinforced with the glans, thus leading to a higher value of Young's modulus.
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Hatzichristou, D., Tzortzis, V., Hatzimouratidis, K. et al. Protective role of the glans penis during coitus. Int J Impot Res 15, 337–342 (2003). https://doi.org/10.1038/sj.ijir.3901039