Anatomical Terminology and Bones PDF

# Anatomical terminology ## Anatomical terms and their meanings | Anatomical term | Meaning | |---|---| | Anterior / In front / Ventral | Near to the front of the body. | | Posterior / Behind / Dorsal | Near to the back of the body. | | Superior / Upper / Cranial | Near to the upper end of body. |...

# Anatomical terminology ## Anatomical terms and their meanings | Anatomical term | Meaning | |---|---| | Anterior / In front / Ventral | Near to the front of the body. | | Posterior / Behind / Dorsal | Near to the back of the body. | | Superior / Upper / Cranial | Near to the upper end of body. | | Inferior / Lower / Caudal | Near to the lower end of body. | | Median | Exactly in the middle line (median plane). | | Medial | Near to the middle line plane. | | Lateral | Away from the middle line plane. | | Proximal | Near to the root of the limb. | | Distal | Away from the root of the limb. | | External / Outer | Towards the surface of a hollowed organ. | | Internal / Inner | Towards the cavity of a hollowed organ. | | Superficial | Towards the skin. | | Deep | Away from the skin. | ## Anatomical positions 1. **Anatomical erect position:** * Human body is standing erect. * Eyes are looking forwards. * Upper limbs are hanging by the sides with the palms facing forwards and the thumbs are directed laterally. 2. **Supine position:** The body lies on its back. 3. **Prone position:** The body lies on its face. 4. **Lateral decubitus position:** The body lies on its side (right or left). 5. **Lithotomy position:** The body lies on its back with flexion of hip and knee. ## Anatomical planes 1. **Median plane (Sagittal):** A median vertical plane which divides the body into equal right and left halves. 2. **Paramedian plane (Para-sagittal):** A vertical plane parallel to the median plane which divides the body into unequal right and left halves. 3. **Coronal (Frontal) plane:** The plane which divides the body into anterior and posterior parts. 4. **Horizontal (transverse) plane:** A transverse plane which devides the body into upper and lower parts. # Fascia * **Definition:** A collection of connective tissue under the skin. * **Types:** Superficial and deep. ## Superficial fascia * **Structure:** 1. A layer of loose connective tissue lies just deep to the skin. 2. It contains a variable amount of fat which is: * More in: females, breast, gluteal region and anterior abdominal wall. * Less in the limbs. * Absent in the eyelid, penis and scrotum. * **Functions:** 1. **Due to the presence of fat:** * Soften the body surface. * Prevents heat loss from the body (thermal insulator). * Facilitates the movement of the skin over the underlying structures. 2. **Contains:** * Nerves, vessels, and lymphatics supplying the skin. * Skin muscles as in face (muscles of expression) and in hand (palmaris brevis). * Special types of glands as mammary glands and superficial lymph nodes. ## Deep fascia * **Structure:** 1. Non-elastic membrane formed of compact regular collagen fibers. 2. Well defined in the limbs (very thick in palm and sole). 3. Absent in the face and in the anterior wall of abdomen. * **Functions:** 1. **Related to muscles:** * Surrounds and separates. * Formation of fibrous sheath surrounding the limb muscles: To help venous return. * Formation of intermuscular septa and interosseous membranes: To separate different muscle groups having different actions and nerve supply. 2. **Related to tendons:** * Formation of Retinacula around wrist and ankle: To keep the tendons in position during movements of joints. In addition to formation of fibrous sheaths around flexor tendons of hands and feet. * Formation of fibrous Raphe where 2 muscles of both sides are inserted into it e.g mylohyoid. → Formation of fibrous pulleys under which a muscle tendon can pass e.g digastric muscle. 3. **Related to vessels and nerves:** * Protection. * Formation of fibrous sheaths around big vessels e.g. Carotid sheath in the neck around common carotid artery and femoral sheath around femoral blood vessels in the lower limb. * Formation of palmar and plantar aponeurosis (in the palm and sole): To protect the underlying vessels, nerves and tendons. ## Internal fascia * **Structure:** CT lining body cavities and extends between the different organs. * **Function:** * Forms strong coats around the organs as fibrous pericardium. * Forms the supporting ligaments for certain organs. * Fixes the internal organs in position. # Cartilage * **Properties:** 1. A hard type of connective tissue which resists compression forces and friction. 2. It has no blood vessels or nerves, so it gets its nutrition by diffusion from the blood vessels of perichondrium. 3. It doesn’t appear in the X-ray films (unless calcified). * **Types:** The cartilage consists of mature cartilage cells (chondrocytes), fibers and matrix (ground substance). According to the different combination of these 3 elements the cartilage is subdivided into 3 types: | Type | Site | Ossification | Cartilage cells | Fibers | Matrix | |---|---|---|---|---|---| | Hyaline cartilage (glass-like) | * Developing bone of fetus * Epiphyseal plates of long bone * Trachea and larynx (except epiglottis) * Articular cartilage of synovial joints. * Sternum (xiphoid process) and costal cartilage | May Occur as in epiphyseal cartilages | Numerous: separate or in groups (cell nest) | Few collagen fibers | Translucent because it has few collagen bundles | | | White Fibrocartilage | * Intervertebral discs * Symphysis pubis. | Does not occur | Few | Rich in collagen fibers | Opaque because it is rich in collagen bundles | | Yellow Elastic cartilage | * Ear pinna and tip of the nose. * Epiglottis of the larynx. * Eustachian tube | Does not occur | Abundant | Rich in elastic fibers | Yellow because it is rich in yellow elastic fibers | ## Pneumatic bones (Paranasal sinuses) * **Site:** * Air filled spaces lying in the skull bones surrounding the nose as: * Frontal sinus: Lies in the frontal bone. * Maxillary sinus: The largest air sinus lying in the maxilla. * Ethmoidal sinuses: 3 groups of sinuses (anterior, middle & posterior) present in the ethmoid bone (in the medial wall of orbit). * Sphenoidal sinus: Lies in the body of sphenoid bone. * **Structure:** Bone containing air cavity. * **Functions:** * Decrease the weight of skull. * Resonance of voice. ## Sesamoid bones * **Site:** Embedded in some muscle tendons e.g. patella which is the largest sesamoid bone embedded in the tendon of quadriceps femoris. * **Structure:** Small nodules of bones. * **Function:** * Supports the tendons subjected to compression forces. * Diminishes the friction between tendons and underlying bones. # Bones * **Structure:** A hard type of connective tissue which forms the skeleton. * **Functions:** * **Calcium:** Stores calcium salts. * **Organs:** Protects the vital organs e.g. the skull protects the brain and thoracic cage protects the heart and lungs. * **Muscles:** Proves a surface area for muscular attachment. * **Movements:** Forms the joints which are responsible for the movement. * **Body:** * Gives a specific shape to the body. * Transmits the body weight e.g. the vertebral column transmits the weight of head and trunk to the pelvis then to the bones of lower limbs and finally to the ground. * **Blood:** Forms the blood elements in the bone marrow. ## Classification 1. **According to their position in the body:** * **Exoskeleton:** Nail, enamel of the teeth. * **Endoskeleton:** * **Axial (central) skeleton:** Skull, mandible, hyoid, sternum, ribs and vertebral column. * **Appendicular (peripheral) skeleton:** Upper and lower limbs. 2. **According to the process of ossification:** * **Intra-membranous ossification:** Occurs in some bones as clavicle and skull cap. The bones develop directly from connective tissue membrane (mesenchymal). * **Intra-cartilaginous ossification:** Occurs in most bones as long bones and vertebrae. The mesenchyme is changed into a cartilage model then the cartilage model is replaced by bone. 3. **According to the shape of bones:** Long bone, short bone, flat bone, irregular bone, sesamoid bone and pneumatic bone. ## Long bones * **Site:** Upper and lower limbs such as humerus and femur. * **Structure:** It's formed of 2 ends (epiphyses) and a shaft (diaphysis) in between. 1. **Epiphysis (upper or lower end):** It consists of spongy (cancellous) bone covered by a thin shell of compact bone. The epiphysis is used for articulation and its articular surface is covered with a layer of hyaline cartilage called articular cartilage. 2. **Diaphysis (Shaft):** * A tube of compact bone with a central medullary cavity which is lined by endosteum and filled with bone marrow. * The shaft is covered with fibrous sheath called periosteum. The long bones increase in width from periosteum. * **Metaphysis:** It lies in the upper and lower parts of the diaphysis of long bone just beneath the epiphyseal cartilage. (It is the most active part of the long bone). 3. **Epiphyseal plate of hyaline cartilage:** It's a plate of hyaline cartilage lying between the epiphysis and diaphysis of the growing long bones. It's responsible for the growth of bone in length. * **Function:** Muscle attachment and movement. ## Short bones * **Site:** Carpal and tarsal bones. * **Structure:** Consist of spongy bone covered with thin layer of compact bone. * **Functions:** They resist compression forces. ## Irregular bones * **Site:** Vertebrae. * **Structure and function:** Like the short bones. ## Flat bones * **Site:** Skull, scapula, sternum and ribs. * **Structure:** Consist of two thin plates of compact bone with a middle layer of spongy bone. * **Functions:** Protection and muscular attachment.