lecture 2

Anatomical Position

Anatomical Position

The standard body position used as a reference for directional terms, where a person stands erect with palms forward and feet parallel.

Directional Terms

Terms used to describe the location of body parts in relation to each other, such as medial, lateral, proximal, and distal.

Body Planes

Divisions of the body into sections, including coronal (front and back), sagittal (left and right), and horizontal (top and bottom).

Human Skeleton

It provides support, movement and mineral storage, is composed of 206 bones, and accounts for 18% of body weight,

Osteogenic Cells

Bone stem cells that divide to produce osteoblasts, essential for bone formation.

Osteoblasts

Bone-building cells that synthesize and secrete collagen and other components of the bone matrix.

Osteocytes

Mature bone cells that maintain bone metabolism and nutrient exchange.

Osteoclasts

Large cells that break down bone tissue, playing a crucial role in bone remodeling.

Compact Bone

Dense bone type that forms the outer layer of bones, providing strength and structure.

Spongy Bone

Lighter bone type found inside bones, consisting of trabeculae and containing bone marrow.

Haversian Canal

Central channel in compact bone that contains blood vessels and nerves.

Trabeculae

Thin columns of bone in spongy bone that provide structural support and house marrow.

Epiphyseal Growth Plate

Cartilage layer in long bones that allows for growth in length during childhood.

Periosteum

Membrane surrounding bones, providing protection and serving as an attachment for tendons and ligaments.

Synovial Joints

Joints that allow for a wide range of movement

Bursae

Fluid-filled sacs that reduce friction between bones and surrounding structures.

Fracture

A break in a bone, which can be classified as complete or incomplete, open or closed.

Osteoporosis

A condition characterized by decreased bone density, leading to increased fracture risk.

Osteoarthritis

A degenerative joint disease caused by wear and tear on cartilage, leading to pain and stiffness.

Rheumatoid Arthritis

An autoimmune condition causing inflammation of the synovium, affecting joints and potentially other organs.

Supine

The body lying face up.

Prone

The body lying face down.

Medial

Nearer to the midline

Lateral

Away from the midline

Bilateral

Both sides

Unilateral

One side

Ipsilateral

On the same side

Contralateral

On the opposite side`

Proximal

Nearer to the trunk

Distal

Further from the trunk

Anterior (ventral)

Nearer the front

Posterior (dorsal)

Nearer the back

Superior

Towards the top

Inferior

Towards the bottom

Coronal / frontal plane

Separating the body front and back.

Sagittal plane

Separating the body left and right.

Horizontal / transverse plane

Separating the body top and bottom.

Haematopoiesis

formation and development of blood cells from the red bone marrow.

Lamellae

Concentric rings of calcified extracellular matrix containing minerals and collagen.

Canaliculi

A mini system of interconnected canals that provides a route for nutrients / waste.

Lacunae

Small spaces called lacunae with osteocytes.

Bone Matrix

The bone matrix is an extracellular framework composed of collagen fibers, with minerals like calcium phosphate, magnesium, and potassium deposited within it. These minerals crystallize and harden, giving bone its strength and hardness.

Long Bones

A type of bone that is longer than it is wide, characterized by a shaft (diaphysis) and two heads (epiphyses), primarily found in the limbs.

Epiphysis

forms the proximal and distal ends of long bones and contains a thin outer region of compact bone covered by articular / hyaline cartilage and inner spongy bone with red bone marrow

Diaphysis

the tubular shaft of long bones. It provides structural support and houses the medullary cavity, which contains yellow bone marrow.

Bone Formation

begins during foetal development, before continuing into childhood and then into adult life. There are two ossification pathways used to produce bone: intramembranous and endochondral ossification.

. Intramembranous ossification

Bone develops from connective tissue sheets. — All flat bones (i.e. skull) and the clavicles .. develop this way.

Endochondral ossification

Bone develops by replacing hyaline cartilage.

Bone Homeostasis

Bones are an important mineral reservoir — mostly calcium. Blood calcium levels have to be tightly controlled to ensure proper blood clotting, nerve and muscle function.

Hypocalcaemia

If blood calcium levels are low

Hypercalcaemia

If blood calcium levels are high

Parathyroid Hormone

increases blood calcium, the activity of osteoclasts (resorption), Stimulates the kidneys to reabsorb and retain calcium in the blood and increases formation of calcitriol which promotes calcium uptake from food in the intestines.

Calcitonin

a hormone that lowers blood calcium levels, it’s secreted by para-follicular cells of the thyroid gland, it inhibits osteoclasts and promotes osteoblast deposition of calcium in the bones. the result is increased bone formation and decreased blood calcium.

Vitamin D

Vitamin D3 aids calcium absorption in the intestines and supports bone turnover, working with vitamin K2. D3 helps absorb calcium into the blood, while K2 activates osteocalcin to direct calcium to the bones.

Axial Skeleton

The axial skeleton, comprising 80 bones, forms the central skeleton and protects vital organs. It includes the skull, inner ear bones, hyoid, thoracic cage, and vertebral column.

Skull

The skull forms the cranium and face, encasing the brain. Its bones are joined by fibrous sutures, with air-filled sinuses that lighten the skull and enhance voice resonance. In infants, fontanelles (soft spots) allow skull flexibility during birth and ossify by 12–18 months.

Vertebral Column

The vertebral column consists of 24 movable vertebrae (7 cervical, 12 thoracic, 5 lumbar) plus the sacrum and coccyx. Vertebrae are named by region and number, with intervertebral discs connecting them. It protects the spinal cord, supports the skull, enables movement, and forms the trunk's axis.

Intervertebral Discs

Intervertebral discs are 23 shock-absorbing structures in the spine (absent in the sacrum) that bind and separate vertebrae. They consist of an outer annulus fibrosus and a gel-like nucleus pulposus, becoming thicker lower down and forming one-third of the spine's length.

Thoracic Cage and Ribs

The thoracic cage consists of the sternum and 12 pairs of ribs. Most ribs connect to the sternum via costal cartilage, while the first rib is positioned behind the clavicle near the lung apex. Ribs 11 and 12, known as floating ribs, lack anterior attachments and connect posteriorly to vertebrae T11 and T12.

Appendicular Skeleton

The appendicular skeleton, comprising 126 bones, includes the limbs and key areas like the shoulder girdle, arms, hands, pelvic girdle, legs, and feet. It facilitates movement and provides organ protection.

Arms and Shoulder

The arms and shoulder consist of the shoulder girdle (clavicle and scapula), humerus (upper arm), ulna (medial forearm), radius (lateral forearm), carpals (wrist), metacarpals (hand), and phalanges (fingers, divided into proximal, intermediate, and distal bones).

Pelvic Girdle

Pelvis = Hip bones + sacrumand coccyx, supporting the weight of the upper body and facilitating locomotion.

Leg

The leg consists of the femur (longest and strongest bone), tibia (shin bone), fibula (lateral lower leg bone), patella (knee cap), tarsals (ankle bones), metatarsals (foot bones), and phalanges (toes).

Muscle Attachments

Muscles that move joints and attach to bones are called skeletal muscles. They connect to bones via tendons, and their contraction generates movement. For example, the Achilles tendon attaches the calf muscle to the ankle.

Joints

Joints connect two bones and allow varying movement. There are 187 joints in the human body, with two types: fibrous joints (limited movement, e.g., skull sutures), and cartilaginous joints (bones connected by cartilage, allowing little to no movement, e.g., growth plates and intervertebral discs).

Synovial Joints

Synovial joints allow the most movement. They have articular cartilage that reduces friction and absorbs shock, and contain synovial fluid, which nourishes the joint through diffusion. Examples include ball-and-socket joints (shoulder, hip) and hinge joints (elbow, knee).

Bone Hormones

Bone hormones regulate growth by balancing osteoblast (bone formation) and osteoclast (bone resorption) activity. Growth hormone, thyroid hormone, estrogen, testosterone, and calcitonin promote osteoblast activity, while parathyroid hormone and cortisol promote osteoclast activity and bone loss.

Bursae

Bursae are fluid-filled sacs that reduce friction between bones and surrounding tissues like muscles, tendons, or skin. They contain connective tissue fluid similar to synovial fluid and are located between skin and bone, tendon and bone, muscle and bone, or ligament and bone.

Flexion

decrease in joint angle._{^{Flexion is a movement that decreases the angle between two body parts, typically occurring at joints such as the elbow or knee.}}

Extension

increase in joint angle._{This movement straightens or extends a joint.}

Rotation

movement around its longitudinal axis. In the limbs it can be medial or lateral (away from the midline). _{It allows the body to pivot or turn, enabling various movements in activities such as twisting or turning.}

Lateral flexion

movement of trunk away from the midline._{The bending of the spine or neck to the side}

Abduction

movement away from midline

Adduction

movement towards midline, _{opposite of abduction.}

Circumduction

circular (flexion, abduction, extension, hyperextension, adduction in succession).

Elevation

superior movement (up).

Depression

inferior movement (down).

Protraction

anterior movement (forward).

Retraction

posterior movement (backward).

Inversion

medial movement of sole (turn in).

Eversion

lateral movement of sole (turn out)

Dorsiflexion

bending foot up._{It involves raising the toes toward the shin.}

Plantar flexion

bending foot down.This movement points the toes away from the leg, increasing the angle between the foot and the front of the leg.

Supination

movement of forearm to turn palm up.

Pronation

movement of forearm to turn palm posteriorly. This motion decreases the angle between the forearm and the palm, rotating the radius over the ulna.

Opposition

movement of thumb across palm to touch fingertips.

Fracture