The back muscles are anatomically layered into superficial (extrinsic) and deep (intrinsic) muscles. The extrinsic back muscles are located in the back, but act to produce movements of the shoulder and assist respiration. The intrinsic back muscles are found deeper to the extrinsic muscles, separated from them by the thoracolumbar fascia. They act exclusively upon the joints of the vertebral column.
Our rock-rolling Sisyphus must've built fabulous back muscles, right? Let's learn their anatomy to see why are they so important Superficial back muscles
The superficial back muscles include the trapezius, latissimus dorsi, levator scapulae, rhomboids and serratus posterior muscles.
Let us introduce you to each of these muscles presented in our diagram.
Trapezius
The trapezius muscle consists of three parts; descending, transverse and ascending. By attaching between the occipital bone, scapula, vertebrae and clavicle, this muscle bounds the nuchal region. Trapezius is supplied by the accessory spinal nerve (CN XI) and anterior rami of C3-C4 via cervical plexus. It moves the scapula and causes extension, lateral flexion and rotation of the head and neck.
The waist
the part of the human body below the ribs and above the hips, often narrower than the areas above and below.
The waist is the part of the abdomen between the rib cage and hips. Normally, the waist is the narrowest part of the torso.
Waistline refers to the horizontal line where the waist is narrowest, or to the general appearance of the waist.
Structure
Because of this and because the waist is often synonymous with the stomach, one can become confused as to the exact location of the waist. Another confusing factor is that the waistline differs on different people. A study showed that self-reported measurements, as opposed to measurement done by a technician, underestimated waist circumference and this underestimation increased with increased body size. In the study, waist circumference measured at the level of the umbilicus was larger than that measured at the natural waist.[1]
To locate the natural waistline, one need simply stand upright and then tilt over to the side, keeping the legs and hips straight. Where the torso creases is the natural waistline.
Waist measurement
obesity-related diseases as high if men have a waist circumference greater than 102 cm (40 in) and women have a waist circumference greater than 88 cm (35 in). Further, whether waist circumference or body mass index (BMI) is a better predictor of adverse health outcomes is debatable. For example, those who lift weights may have high BMI but are at relatively low risk for cardiovascular consequences. For these people, waist circumference may be a better indicator of overall health. Some research suggests waist circumference can be predicted from brain function, therefore capturing the neurobehavioral pathophysiology of obesity.
An extremally high waist circumference can lead to falsely low estimates of bone health when using the trabecular bone score.
Waist hip ratio
Waist–hip ratio is the ratio of the circumference of the waist to that of the hips. It measures the proportion by which fat is distributed around the torso. Waist–hip ratios of 0.7 for women and 0.9 for men have been shown to correlate strongly with general health and fertility[citation needed]. This shape is compared to the hourglass shape of women.
Waist reduction and training
Waist reduction or waist training refer to the act of wearing a corset or other constricting garment to reduce or alter the waistline. The four floating ribs may be permanently compressed or moved by such garments. A girdle may also be used to alter the appearance of the waist.
Waist reduction may be used simply to reduce the width of the waist. This change can be permanent or temporary.
Waist training may be used to achieve a certain permanent waist shape, such as a pipe-stem waist.
Reproductive part the penis and vagina
Erections can occur in non-sexual situations; spontaneous non-sexual erections frequently occur during adolescence and sleep. In its flaccid state, the penis is smaller, gives to pressure, and the glans is covered by the foreskin. In its fully erect state, the shaft becomes rigid and the glans becomes engorged but not rigid. An erect penis may be straight or curved and may point at an upward angle, a downward angle, or straight ahead. As of 2015, the average erect human penis is 13.12 cm (5.17 in) long and has a circumference of 11.66 cm (4.59 in).[2][3] Neither age nor size of the flaccid penis accurately predicts erectile length.
Structure of penis
Three main parts of the human penis include:
Root: It is the attached part, consisting of the bulb in the middle and the crura, one crus on either side of the bulb. It lies within the superficial perineal pouch. The crus is attached to the pubic arch.
Shaft: The pendulous part of the penis. It has two surfaces: dorsal (posterosuperior in the erect penis) and ventral or urethral (facing downwards and backwards on the flaccid penis). The ventral surface is marked by the penile raphe. The base of the shaft is supported by the suspensory ligament, which is attached to the pubic symphysis.[5]
Epithelium of the penis consists of the shaft skin, the foreskin (prepuce), and the preputial mucosa on the inside of it. The foreskin covers and protects the glans and shaft. The epithelium is not attached to the underlying shaft, so it is free to glide to and fro.
spongiosum form the bulb and the distal ends form the glans penis.
The enlarged and bulbous-shaped end of the corpus spongiosum forms the glans penis with two specific types of sinusoids, which supports the foreskin, a loose fold of skin that in adults can retract to expose the glans.The area on the underside of the glans, where the foreskin is attached, is called the frenulum. The rounded base of the glans is called the corona. The inner surface of the foreskin and corona is rich in sebaceous glands that secrete smegma. The structure of the penis is supported by the pelvic floor muscles.
The urethra, which is the last part of the urinary tract, traverses the corpus spongiosum (spongy urethra), and its opening, known as the urinary meatus, lies on the tip of the glans. It is a passage both for urine and for the ejaculation of semen.
Reproduction.It is a remnant of the baculum that has likely evolved due to change in mating practice.
The human penis cannot be withdrawn into the groin, and it is larger than average in the animal kingdom in proportion to body mass. The human penis is reciprocating from a cotton soft to a bony rigidity resulting from penile arterial flow varied between 2–3 to 60–80 mL/Min implies the most ideal milieu to apply Pascal's law in the entire human body; the overall structure is unique.
Size
Among all primates, the human penis is the largest in girth, but is comparable to the chimpanzee penis and the penises of certain other primates in length.
Penis size is affected by genetics, but also by environmental factors such as fertility medication and chemical/pollution exposure.
Normal variation
located at the sebaceous glands and are normal.
Phimosis is an inability to retract the foreskin fully. It is normal and harmless in infancy and pre-pubescence, occurring in about 8% of boys at age 10. According to the British Medical Association, treatment (topical steroid cream and/or manual stretching) does not need to be considered until age 19.
Curvature: few penises are completely straight, with curves commonly seen in all directions (up, down, left, right). Sometimes the curve is very prominent but it rarely inhibits sexual intercourse. Curvature as great as 30° is considered normal and medical treatment is rarely considered unless the angle exceeds 45°. Changes to the curvature of a penis may be caused by Peyronie's disease.