Introduction to Human Anatomy

Introduction to Human Anatomy

• Anatomy is the science that studies the structures of body parts and their relationships

How to Study Anatomy

• Learning anatomy involves theoretical study, practical application, and clinical relevance.

Definition of Anatomy

• Anatomy is derived from the Greek word "Anatom," meaning "cut up" or dissection.

Division of Anatomy

• Anatomy is divided into: Gross anatomy, Microscopic anatomy, Developmental anatomy, Surface anatomy, and Clinical anatomy

Gross or Macroscopic Anatomy

• Definition: The study of structures that can be seen with the naked eye.
• Types:
  • Regional anatomy refers to studying the body area by area.
  • Systemic anatomy refers to studying the body system by system.

Microscopic Anatomy

• Definition: Study of structures that can be seen using a microscope.
• Types:
  • Cytology is the study of cells.
  • Histology is the study of tissues.
  • Organology is the study of organs.
• Cells form tissues, tissues form organs, organs form systems, and systems form organisms.

Developmental Anatomy

• Definition: Study of anatomical changes that occur throughout a life cycle.
• Types:
  • Embryology focuses on prenatal development.
  • Postnatal development involves the study of structures after birth.
  • Ontogeny is the total development of an individual.

Surface Anatomy

• Definition: The study of external body features and their relationships to underlying structures.

Clinical Anatomy

• Definition: The application of anatomical knowledge in a clinical setting.

The Anatomical Position

• The body is standing upright (or erect).
• The face and eyes are forward.
• The upper limbs are at the sides.
• The palms are facing forward.
• The lower limbs are parallel.
• The toes are facing forward.

Planes of the Body

• Median Plane: A vertical plane that passes through the center of the body, dividing it into equal right and left halves.
• Sagittal Plane: Any plane parallel to the median plane that divides the body into unequal right and left portions.
• Coronal (Frontal) Plane: A vertical plane situated at a right angle to the median plane, dividing the body into anterior (front) and posterior (back) portions.
• Horizontal Plane: Lies at right angles to both the median and the coronal planes and divides the body into upper and lower parts.
• Transverse Plane: Lies perpendicular to the long axis of a given structure and divides that structure in a cross-section orientation.

Terms of Positions

• Anterior (ventral): Refers to the front of the body (e.g. the nose is on the anterior side of the head).
• Posterior (dorsal): Refers to the back of the body (e.g. the buttocks are on the posterior side of the body).
• Superior (cranial or cephalic): Refers to structures situated nearer the head (e.g., the head is at the superior end of the body).
• Inferior (caudal): Refers to structures situated nearer the feet (e.g., the feet are at the inferior end of the body).
• Medial: Refers to structures situated nearer to the median plane of the body.
• Lateral: Refers to structures situated farther away from the median plane of the body. (e.g., in the head, the eyes are lateral to the nose).
• Proximal: Refers to structures situated nearer the root of the limbs (e.g. in the upper limb, the shoulder is proximal to the elbow).
• Distal: Refers to structures situated far away from the root of the limbs (e.g., the hand is distal to the elbow).
• Superficial: Refers to structures situated nearer the skin or the surface of the body (e.g., the skin is superficial to the ribs).
• Deep: Refers to structures situated further away from the skin or the surface of the body (e.g., the heart is deep to the ribs).
• Internal: Refers to the inside of the structure or space (e.g. the lung).
• External: Refers to the outside of the structure or space (e.g. the skin).
• Palmar: Replace "anterior" in the hands.
• Dorsal: Replace "posterior" in the hands.
• Dorsum: Replace "superior" in the feet.
• Plantar: Replace "inferior" in the feet.
• Ipsilateral: Structures on the same side of the body.
• Contralateral: Structures on opposite sides of the body.
• Tibial: Refers to medial in the leg.
• Fibular: Refers to lateral in the leg.
• Supine: The body is lying on the back.
• Prone: The body is lying on the abdomen.

Terms Related to Movements

• In the Trunk:
• Flexion: Movement of the trunk anteriorly in the sagittal plane.
• Extension: Bending posteriorly.
• Lateral Flexion: Movement of the trunk in the coronal plane.
• In the Limbs:
• Flexion: Movement that takes place in a sagittal plane, usually anterior movement, but occasionally posterior in the knee joint.
• Extension: Means straightening of the joint and usually takes place in posterior direction.
• Abduction: Movement away from the midline in the coronal plane.
• Adduction: Movement toward the midline in the coronal plane.
• In the Wrist:
• Abduction (Radial Deviation): Movement of the hand toward the radial side (thumb).
• Adduction (Ulnar Deviation): Movement of the hand toward the ulnar side (little finger).
• In the Ankle Joint:
• Dorsiflexion: Movement toward the dorsum of the foot.
• Plantar Flexion: Movement toward the sole of the foot.
• In the Fingers and Toes:
• Abduction: Spreading of fingers or toes.
• Adduction: Drawing together of fingers or toes.
• In the Thumb:
• Abduction: Movement in the anteroposterior plane away from the palm.
• Adduction: Movement in the anteroposterior plane toward the palm.
• Flexion: Movement in the coronal plane toward the palm.
• Extension: Takes place in the coronal plane away from the palm.
• Opposition: Movement of the thumb across the palm where the anterior surface of its tip comes into contact with the anterior surface of the tip of any other finger.
• Rotation:
• Medial (Internal) Rotation: Movement that causes the anterior surface of the part facing medially.
• Lateral (External) Rotation: Movement that causes the anterior surface of the part facing laterally.
• Supination of Forearm: A lateral rotation, so the palm faces anteriorly.
• Pronation of Forearm: A medial rotation, so the palm faces posteriorly.
• Circumduction: A sequence of flexion, extension, abduction, and adduction.
• In the Foot:
• Inversion: Movement by which the sole is turned to face medially and the medial border of the foot is raised.
• Eversion: The opposite movement to inversion.

Basic Anatomical Structures

• Basic anatomical structures include skin, fasciae, vessels, nerves, muscles, bones, and joints.

Skin

• The skin consists of: Epidermis and Dermis.
• Epidermis:
  • The superficial layer is made of stratified squamous epithelium.
  • The epidermis is very thick on the palm and sole to withstand wear and tear.
• Dermis:
• A deeper vascular, dense fibrous tissue with small protrusions that send to the epidermis.
• The dermis is composed of dense connective tissue, containing blood vessels, lymph vessels, and nerves.
• In the dermis, bundles of collagen fibres arranged in parallel rows are called cleavage lines.
• Folds of the skin over joints are known as skin creases.

Fasciae

• Divided into two types, superficial and deep.
• Superficial Fascia:
• A mixture of loose areolar and adipose tissue uniting the dermis to the underlying deep fascia.
• Thickness varies, thin in the eyelid but dense in the scalp, back of the neck, palms, and soles.
• It also contains small arteries, veins, lymph vessels and nerves of the skin, as well as lymph nodes in it.
• Deep Fascia:
• A membranous layer of connective tissue that invests the muscles and other deep structures.
• Around joints, the deep fascia may thicken to form a retinaculum, holding underlying tendons in position or acting as pulleys.
• In the limbs, it sends septa between the muscles, called intermuscular septa.

Vessels

• Divided into blood vessels and lymph vessels.

• Blood Vessels:

  • Arteries carry blood from the heart to the tissues.
  • The largest artery is the aorta, about 2.5 cm in diameter.
  • Smallest arteries (less than 0.1 mm) are arterioles, which transmit blood to the capillaries.

• The union of branches of arteries is called anastomosis, especially around the joints of limbs, gastrointestinal tract, and base of the brain.

• Union of branches of arteries important for maintaining circulation when one artery is blocked, so the remaining arteries enlarge and produce collateral circulation.

• Terminal branches of vessels not anastomosing with adjacent areas are known as end arteries.

• Blood Capillaries consist of Microscopic tubes forming a network discharge through which arterioles blood smallest in to tributaries of veins.

• Capillary walls consist of a single layer of cells which endothelial exchange substances between the blood and tissues.

• Veins are vessels that collect blood from the tissues back to the heart.

• Many veins have valves while the smallest veins are called venules.

• Medium-sized deep arteries are often accompanied by two or more veins (venae comitantes).

• Lymph Vessels:

  • Lymph, a tissue fluid, is collected from tissues by lymph capillaries, to form a network.
  • These capillaries unite to form small lymph vessels and these unite again to form large lymph vessels which have many valves.
  • Lymph is drained to the bloodstream at the root of the neck, through lymph nodes.
  • Lymph vessels carry lymph to the lymph nodes (afferent vessels).
  • Lymph vessels carry lymph away the lymph nodes (efferent vessels).
  • Lymph nodes: Gland-like structures which act filter for the lymph, they vary in size, and they increase in size in case of inflammation or tumors.

Nerves

• Whitish cords consisting of nerve fibres of variable diameter held together by fibrous tissues.
• Each nerve is surrounded by a dense connective tissue sheath called the epineurium.
• Inside the epineurium are bundles of nerve fibers surrounded by a connective tissue sheath called the perineurium; between individual nerve fibers is loose connective tissue called the endoneurium.
• A nerve cell plus its processes is known as a neuron.
• Each cell has a cell body from which one or more processes called neurites project.
• Neurites responsible for receiving information and conducting it toward the cell body are called dendrites.
• The single long neurite that conduct impulses away from the cell body is called the axon.
• Dendrites and axon are often called nerve fibers.
• A segmented sheath, called myelin sheath, surrounds the nerve fibre.
• When the myelin sheath is absent the nerve fiber is classified as nonmyelinated nerve fiber.
• Accumulation of cell bodies outside the central nervous system (CNS) are called ganglion
• Nerve fibres transmit impulses from the CNS to structures of the body, these make the muscles to contract and are called efferent or motor nerve fibres.
• Fibers that carry impulses to the CNS carry information after stimulation and called afferent or sensory nerve fibres.
• Nerves classified as to Cranial and Spinal.
• Cranial nerves: Their nuclei located in the brain and 12 pairs emerge through foramina in the skull.
• Spinal nerves: There are 31 pairs.
  • 8 cervical (C1-C8)
  • 12 thoracic (T1-T12)
  • 5 lumber (L1-L5)
  • 5 sacral (S1-S5)
  • 1 coccygeal
• The typical spinal nerve has two roots (anterior and posterior).
• The anterior root: Bundles of nerve fibers carry impulses away from the CNS and called is efferent fibers (motor fibers), cause contraction of skeletal muscles.
• The posterior root: Bundles of nerve fibers that carry impulses toward the CNS and called is afferent fibers (sensory fibers), convey information about sensation as of pain, touch, temperature and vibration.
• The cell bodies of posterior roots are located in swelling on their root, called posterior root ganglion.
• The strip of skin supplied by a single spinal nerve dermatome.
• The total mass of the muscles supplied by a spinal nerve myotome.
• The anterior rami of the cervical and thoracic spinal nerves and form the cervical and brachial plexus.
• The anterior rami of lumbar, sacral and coccygeal nerves, form lumbar, sacral and coccygeal plexuses.

Muscles

• Skeletal muscles produce body movements and are voluntary.
• Skeletal muscles normally have two or more attachments where attachment moves the least call as to called origin while attachment that moves is called as insertion.
• The fleshy fleshy part of a muscle is knows as the belly and ends made as made of tendons.
• Flattened muscles such as abdominal muscles are attached by means of the fibrous sheet called the aponeurosis.
• The histological muscle unit or muscle fiber, are united tissue a by by a areolar connective muscle by cover outer the that epimysium is The fiber.
• Muscle fibres to or parallel arranged fibres the when arrangement oblique be arranged to the is called muscle is arranged muscle direction according.
• Unipennate: the run fibres muscles and side one on lies tendon.
• The lies oblique muscles centre the while faces each two sides the is tendon face.
• From centre tendon with muscles faces each.
• Motor fibres by muscles face fibres are face are by faces by also are to face and smooth vessels blood make face.
• Smooth muscles spindle long of consists fibres elastic of. vessels elastic bladder. elastic vessels elastic etc, fibres elastic by supplied are and fibres automatic are those faces are.
• Cardiac muscle is of myocardium face face etc, face by of is fibres face the elastic is of face smooth the of face.

Bones

• They are living tissues consisting of cells, fibers, and matrix, hard due to calcification of the extracellular matrix.
• The skull, vertebral column protect the CNS, other bones lever function e.g. long bones act as of limbs.
• Compact bones are bones.
• Cancellous Bones are that.
• Soft is marrow bones inner faces.
• All surfaces all over.
• Epiphyseal regions broadness with is bones that of faces of.
• Humerus broadness bone which of etc, broadness areas middle faces regions of of the which broadness bone faces the.
• Extremity areas broadness faces the faces areas middle that of faces are faces areas middle faces the.
• Which bones cuboidal are faces of of faces to in broadness and faces which cuboidal are faces the. faces which short are in face.

Joints

• They are where two or more bones together, whether not.
• Joints in joints of and joints, joints are and fibrous which, in face and to bones between joints of.
• Fibrous to face that which bones to a of bones area face.
• The that is to that faces of and and face faces area with faces to cartilage face bones faces area with is that faces.
• Face the for of that face which as of bones is and plate bones is which of faces.
• Cartilage in which of faces.
• Here with to the at are plates covering where face which The are surface and which plate, are at faces to