Embryology and Early Development

Chick Embryo Development

Embryology explores the development of organisms from fertilization to birth. The chick embryo is a classic model for studying vertebrate development due to its accessibility and similarity to human embryogenesis.

• Stages of Development: Early stages include the zygote, 2-cell stage, and blastula/blastocyst.

• Key Structures: Extra-cellular matrix, polar bodies, cortical vesicles, and nucleus are important for fertilization and early cell division.

• Color Coding in Models:

  • Yolk: Yellow

  • Yolk sac: Pink/salmon

  • Blastula/blastocyst wall: Blue

  • Inner cell mass/future baby: Violet

• Somites: Segmented blocks of mesoderm that give rise to vertebrae and skeletal muscle. In a 24-hour chick embryo, approximately 24 somites are visible.

Example: In a cross-section of a chick embryo, label the ectoderm, endoderm, mesoderm, neural tube, and somite. The yolk sac is prominent because the embryo is not yet tube-shaped.

Skeletal System: Bones and Palpation

Skull Anatomy

The skull protects the brain and forms the structure of the face. Palpation helps identify key landmarks for clinical and anatomical study.

• Key Bones: Frontal, parietal, temporal, occipital, sphenoid, ethmoid.

• Important Landmarks:

  • Sagittal suture: Joint between parietal bones.

  • External protuberance of occipital: Bony bump at the back of the skull.

  • Mastoid process: Projection of the temporal bone behind the ear.

Vertebral Column

The vertebral column supports the body and protects the spinal cord. It consists of cervical, thoracic, lumbar, sacral, and coccygeal regions.

• Spinous processes: Posterior projections for muscle attachment.

• Transverse processes: Lateral projections for muscle and ligament attachment.

• Prominent vertebra: C7 (vertebra prominens).

Thoracic Cage and Pectoral Girdle

The thoracic cage protects vital organs and provides attachment for muscles involved in respiration and upper limb movement.

• Clavicle: Collarbone connecting sternum and scapula.

• Scapula: Shoulder blade with spine, acromion, and coracoid process.

• Humerus: Upper arm bone with greater and lesser tubercles.

• Ulna and Radius: Forearm bones; ulna forms the elbow, radius allows wrist rotation.

• Carpal bones: Wrist bones including pisiform and scaphoid.

Pelvic Girdle and Lower Limb

The pelvic girdle supports the weight of the upper body and protects pelvic organs.

• Ilium, ischium, pubis: Three bones forming the hip.

• Femur: Thigh bone, largest in the body.

• Tibia and Fibula: Lower leg bones; tibia is medial and weight-bearing, fibula is lateral.

• Patella: Kneecap, protects the knee joint.

• Metatarsals: Foot bones; 5th metatarsal is lateral.

Ligaments of the Upper and Lower Extremities

Upper Extremity Ligaments

Ligaments stabilize joints and guide movement. The upper limb contains several important ligaments for mobility and strength.

• Glenoid fossa to anatomical neck of humerus: Stabilizes shoulder joint.

• Ulnar collateral ligament: Medial epicondyle of humerus to ulna; stabilizes elbow.

• Annular ligament: Surrounds head of radius; allows rotation.

• Radial collateral ligament: Lateral epicondyle of humerus to annular ligament.

• Flexor retinaculum (transverse carpal ligament): Forms carpal tunnel.

• Extensor retinaculum: Stabilizes extensor tendons of the hand.

Lower Extremity Ligaments

Lower limb ligaments provide stability for weight-bearing and movement.

• Capsule of the hip: Surrounds femoral neck, attaches to acetabulum.

• Medial (tibial) collateral ligament: Medial epicondyle of femur to tibia; stabilizes knee.

• Lateral (fibular) collateral ligament: Lateral epicondyle of femur to head of fibula.

• Lateral collateral ligament of the ankle: Lateral malleolus to talus and calcaneus.

• Linea alba: Fibrous structure from xiphoid process to pubic symphysis; important for abdominal wall integrity.

Cellular Respiration

Stages and Key Features

Cellular respiration is the process by which cells generate ATP from nutrients. It consists of glycolysis, the transition stage, Krebs cycle, and electron transport.

Key Equation:

Additional info: Without oxygen, pyruvate cannot enter the Krebs cycle, and ATP production is greatly reduced.

Integumentary System

Layers of the Skin

The integumentary system protects the body and regulates temperature. It consists of multiple layers and accessory structures.

• Epidermis: Outermost layer, includes stratum corneum, lucidum, granulosum, spinosum, and basale.

• Dermis: Middle layer, contains papillary and reticular layers.

• Hypodermis: Deepest layer, composed of adipose tissue.

Key Structures and Cells

• Sebaceous gland: Produces sebum for lubrication.

• Sweat gland: Produces sweat for thermoregulation.

• Arrector pili: Muscle causing hair to stand up.

• Hair follicle: Structure from which hair grows.

• Melanocyte: Produces melanin pigment.

• Dendritic cell: Immune cell in the skin.

• Dermal papilla: Projections increasing surface area for exchange.

Skin Accessories

• Hair shaft: Visible part of hair above skin.

• Hair root: Part of hair below skin surface.

• Hair bulb: Base of hair follicle.

• Hair papilla: Provides nutrients to growing hair.

Example: The stratum basale is the deepest layer of the epidermis and contains stem cells for skin regeneration.