Human Anatomy: Bones, Muscles, and Nervous System

Posted on Dec 4, 2024 in Biology

Human Body Planes

Midsagittal Plane

Cuts the human figure in the anatomical position from top to bottom and front to back through the midline of the body, dividing it into two equal and symmetrical halves.

Medio-frontal Plane

Cuts the human figure from top to bottom and side to side, separating it into two parts: anterior (front) and posterior (back).

Mid-horizontal Plane

Cuts the human figure at waist/navel height, running from front to back. The upper part is called superior and the lower part is called inferior.

Skull Bones

  • Occipital (1): Located at the back of the head, in the neck.
  • Frontal (1): Located at the front of the head.
  • Temporal (2): Located above the ears.
  • Parietal (2): Located on the top of the head.
  • Sphenoid (1): Located between the temporal and frontal bones.

Bones of the Spine

  • Cervical (7): The first is called the atlas (C1) and the second is called the axis (C2). They are named C1-C7.
  • Thoracic (12): Located below the neck and are named T1-T12.
  • Lumbar (5): Located below the thoracic vertebrae and are named L1-L5.
  • Sacrum (1): Located below the fifth lumbar vertebra; forms the back of the pelvis.
  • Coccyx (1): Located below the sacrum; the last bone of the spine.

Bones of the Chest

Twelve pairs of ribs (7 true, 3 false, and 2 floating) are attached to the sternum by cartilage. They form the rib cage along with the sternum and thoracic vertebrae. The last two pairs do not join the sternum and are called floating ribs.

Bones of the Upper Limb

  • Scapula (2): Part of the shoulder, back, and upper chest.
  • Clavicle (2): Located between the sternum and scapula.
  • Humerus (2): The bone of the upper arm.
  • Ulna (2): The inner bone of the forearm.
  • Radius (2): The outer bone of the forearm.
  • Carpals (8): The bones of the wrist.
  • Metacarpals (10): The bones of the palm.
  • Phalanges (28): The bones of the fingers; each finger has 3 phalanges except the thumb, which has 2.

Bones of the Lower Limb

  • Femur (2): The bone of the thigh.
  • Patella (2): Located in front of the knee.
  • Tibia (2): The inner bone of the lower leg, below the femur.
  • Fibula (2): The outer bone of the lower leg, behind the tibia.
  • Tarsals (7): The bones of the ankle and heel.
  • Metatarsals (10): The bones of the foot, connecting the tarsals to the phalanges.
  • Phalanges (28): The bones of the toes; each toe has 3 phalanges except the big toe, which has 2.

Joints

Joints are the support points of the bony levers. They allow movement, hold bones together, and prevent their separation.

  • Synarthrosis: An immovable joint found predominantly in the skull and face.
  • Amphiarthrosis: A slightly movable joint found predominantly in the spine and pubic symphysis.
  • Synovial Joint: A freely movable joint found predominantly in the shoulder, wrist, and knee.

Muscles

Muscles are the active organs of motion and have the property of contraction. There are three types:

  • Skeletal Muscles: Muscles that can be moved voluntarily.
  • Smooth Muscles: Muscles that move involuntarily, such as those in the digestive tract and blood vessels.
  • Cardiac Muscle: The muscle tissue that forms the heart.

Central Nervous System

Consists of the brain and spinal cord.

Brain

Contains internal cavities called ventricles filled with cerebrospinal fluid. It has the following parts:

  • Cerebrum: Has two hemispheres (right and left). The outer layer, called the cerebral cortex, has folds separated by furrows. The cerebral cortex is the main center for integrating sensory information and muscle commands. Its functions are sensory, motor, and integration.
  • Diencephalon: Divided into three areas: the corpus callosum, the thalamus, and the hypothalamus.
  • Cerebellum: Responsible for balance, coordination, and motor action.
  • Brainstem: Includes the midbrain, pons, and medulla oblongata.

Spinal Cord

Located in the spinal canal of the vertebral column. It is composed of nerve cords running upward and downward, connecting the higher nerve centers with the rest of the body.

Peripheral Nervous System

Consists of twelve pairs of cranial nerves that exit the brain and thirty-one pairs of spinal nerves that exit the spinal cord through openings between the vertebrae.

Definitions

Groove (Sulcus):
A depression in the brain.
Fissure:
A deeper groove that divides the brain into lobes.
Sagittal Fissure:
Divides the brain into two hemispheres (right and left).
Bradycardia:
Heart rate below 60 beats per minute.
Tachycardia:
Heart rate over 100 beats per minute.
CPR (Cardiopulmonary Resuscitation) = BLS (Basic Life Support):
A lifesaving technique used when someone’s breathing or heartbeat has stopped.
Advanced CPR (ACLS – Advanced Cardiac Life Support):
Advanced life support measures for cardiopulmonary arrest.
Tracheotomy:
An incision in the trachea to remove foreign bodies, treat local lesions, or obtain a biopsy sample.
Cerebrospinal Fluid (CSF):
Fluid that bathes the brain and spinal cord; located between the pia mater and arachnoid mater.
Epidural Space:
The space between the dura mater and the bone.
Synapse:
The connection point between two nerve cells where nerve impulses are transmitted; involves chemicals called neurotransmitters, which can be excitatory or inhibitory.
Sclerosis:
Hardening of an organ or tissue due to increased connective tissue.
Lumbar Puncture:
A procedure to extract cerebrospinal fluid from the subarachnoid space. It is performed at the level of L4 to avoid injury to the spinal cord.
Meninges:
The three membranes that protect the central nervous system:
  • Dura Mater: The outer layer.
  • Arachnoid Mater: The middle layer, responsible for distributing cerebrospinal fluid.
  • Pia Mater: The inner layer.