Category Archives: Phil’s Anatomy

What Are Human Bones Made Of?

Human bone is a living, growing tissue. Bone tissue (or osseous tissue) is a type of dense connective tissue composed mainly of collagen (or ossein fibers) and bone cells called osteocytes.

There are two types of bone tissue: cortical bone and cancellous bone.

  • Cortical bone (compact bone) forms the extremely hard, strong, stiff and dense exterior of bones and facilitates the main function of bones: to support the whole body, protect organs, provide levers for movement, and store and release chemical elements, mainly calcium. Cortical bone makes up 80% of the weight of a human skeleton.
  • Cancellous bone (trabecular or spongy bone) is softer and weaker than cortical bone, but is considerably more flexible. Typically found at the ends of long bones (near joints and within the interior of vertebrae), cancellous bone is highly vascular and frequently contains red bone marrow where haematopoiesis (the production and maturation of blood cells) occurs.

Bone tissue is covered by the periosteum – a dense membrane layer of vascular connective tissue consisting of an outer fibrous layer and an inner cellular layer (cambium).

  • The outer layer is composed mostly of collagen and contains nerve fibers that cause pain when the tissue is damaged. It also contains many blood vessels – branches of which penetrate the bone to supply the osteocytes (bone cells). These perpendicular branches pass into the bone along channels known as Volkmann canals to the vessels in the haversian canals, which run the length of the bone. Fibers from the inner layer also penetrate the underlying bone, assisting the blood vessels to bind the periosteum to the bone.
  • The inner layer of the periosteum contains osteoblasts (bone-producing cells) and is most prominent in fetal life and early childhood, when bone formation is at its peak. In adulthood these cells are less evident, but they retain their functional capacities and are vital to the constant remodeling of bone that goes on throughout life.

Female Body Shapes

There are six basic “shape “categories that female bodies fall into:

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Hourglass This shape is often referred to as the perfect shape.

  • Bust and hips are well balanced.
  • Small, defined waist.
  • Rounded shoulders that align with hips.
  • Upper body is proportionate in length to legs.

Inverted Triangle Known as the second best body shape (after the hourglass) the inverted triangle is often called the top-heavy V shape.

  • Large bust.
  • Broad shoulders.
  • Narrow hips.

Triangle – The triangle (or pear) shape, is when the lower body is larger than the top.

  • Narrow shoulders.
  • Heavy rear.
  • Heavy thighs.

Rectangle – Rectangle shapes are when chest and hip-lines are the same width.

  • No waist definition.
  • Arms and legs are proportionally slender.
  • Women with a rectangle shape have small to medium breasts and flat bottoms.

Oval – Oval (or apple) body shapes tend to have a full, undefined midsection. The stomach area is low. You might have “love handles.” The hips are wide and upper thighs thick.

  • Full face.
  • Short neck.
  • Large bust.
  • Narrow hips.
  • Slender legs.

Diamond – Diamond shapes have wide hips and full midsections.

  • Hips are broader than bust and shoulders.
  • Waist is the widest part of overall frame.
  • Thick upper legs.
  • Proportionate slender arms.

Body Types

There are three basic human body types:

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Ectomorph distinguished by a lack of fat and muscle tissue.

  • Thin face with high forehead and receding chin.
  • Narrow chest, clavicle, abdomen and hips.
  • Long, thin arms and legs with small wrists and ankles.
  • Low body fat and very little muscle.

Mesomorph – marked by a well-developed musculature.

  • Large square head.
  • Wide clavicle.
  • Broad, muscular chest and shoulders.
  • Heavily muscled arms and legs.
  • Narrow waist.
  • Minimal body fat.
  • Tends to develop muscle easily.

Endomorph characterized by a preponderance of body fat.

  • Blocky build.
  • Round head.
  • Thick rib cage.
  • Large, round abdomen.
  • Short arms and legs with fat upper arms and thighs.
  • Slender wrists and ankles.
  • Hips as wide (or wider) than clavicle.

Muscles Of The Hip

The hip is one of the most flexible joints in the entire human body. The many muscles of the hip provide movement, strength, and stability to the hip joint and the bones of the hip and thigh. These muscles can be grouped based upon their location and function. The four groups are the anterior group, the posterior group, adductor group, and the abductor group.

The anterior muscle group features muscles that flex (bend) the thigh at the hip. These muscles include the iliopsoas group (which consists of the psoas major and iliacus muscles) and  the quadriceps femoris group (which consists of the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis).

The posterior muscle group is made up of the muscles that extend (straighten) the thigh at the hip. These muscles include the gluteus maximus muscle (the largest muscle in the body) and the hamstrings group (which consists of the biceps femoris, semimembranosus, and semitendinosus muscles). Climbing stairs, standing, walking, and running are all activities that require strong contractions from the posterior muscle group to extend the leg.

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The adductor muscle group, also known as the groin muscles, is a group located on the medial side of the thigh. These muscles move the thigh toward the body’s midline. Included in this group are the adductor longus, adductor brevis, adductor magnus, pectineus, and gracilis muscles. Overstretching of these muscles caused by rapid lateral movement the thigh can lead to a groin pull, a common sports injury.

The abductor muscle group is located on the lateral side of the thigh and moves the thigh away from the body’s midline. These muscles include the piriformis, superior gemellus, inferior gemellus, tensor fasciae latae, sartorius, gluteus medius, and gluteus minimus muscles. Spreading the legs to do a split is an example of a movement involving the abductor muscles.

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Abdominal Muscles

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The rectus abdominis is the large muscle in the mid-section of the abdomen. It enables the tilt of the pelvis and the curvature of the lower spine.

Located next to the rectus abdominis (on each side of the body) and beneath the external oblique is the internal oblique muscle. Originating at the lumbar fascia (a connective tissue that covers the lower back), the outer portion of the inguinal ligament (a ligament located on the bottom-outer edge of the pelvis), and back of the iliac crest (the upper-outside portion of the pelvis), the internal oblique muscles end at the bottom edge of the rib cage, the rectus sheath (fibrous tissue that covers the abdominal muscles) and the pubic crest (an area in the lower-front of the pelvis). Located closer to the skin than the transverse abdominal muscle, the internal obliques support the abdominal wall, assist in forced respiration, aid in raising pressure in the abdominal area, and help rotate the trunk.

Also situated on each side of the body, are the largest and the most superficial (outermost) of the three flat muscles of the lateral anterior abdomen: the external obliques. Extending from the lower half of the ribs down to the pelvis, the external oblique muscles (together) cover the sides of the abdominal area, help rotate the trunk, pull the chest (as a whole) downwards (which compresses the abdominal cavity), and supports the rotation of the spine.

The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) the internal oblique muscle. Named for the direction of its fibers, the transverse abdominal is the innermost of the flat muscles of the abdomen, helps to compress the ribs and viscera (the internal organs in the abdominal cavity), and provides thoracic and pelvic stability.

The Trapezius

The trapezius is a major muscle of the back comprised of two large, wide, and flat superficial muscles that are responsible for moving, rotating, and stabilizing the scapula (shoulder blade) and extending the head at the neck.

Extending longitudinally from the occipital bone (a saucer-shaped membrane bone that is the main bone of the occiput and is situated at the back and lower part of the skull) to the lower thoracic vertebrae and laterally to the spine of the scapula, the functions of the trapezius are to move the scapulae and support the arm.