Human Anatomy: Unit One (Muscular System)

Muscle Structure

• A sarcomere is a functional unit of muscle tissue, composed of myofibrils, I bands, and A bands.
• Myofibrils are made up of myofilaments, which contain actin and myosin proteins.
• The sarcolemma is the plasma membrane of a muscle fiber, and it surrounds the sarcoplasmic reticulum, which stores and releases calcium ions to regulate muscle contraction.
• T-tubules are invaginations of the sarcolemma that allow for rapid transmission of action potentials.
• Mitochondria are found within muscle fibers and provide energy for muscle contraction.

Neuromuscular Junction

• The neuromuscular junction is the site where a motor neuron terminates and forms a synapse with a muscle fiber.
• The endomysium is a layer of connective tissue that surrounds individual muscle fibers.

Sweat Glands

• Apocrine and eccrine sweat glands are two types of sweat glands found in the skin.
• Apocrine glands are larger and more complex, while eccrine glands are smaller and more numerous.

Integumentary System

• The epidermis is the outermost layer of the skin, composed of stratified squamous epithelium.
• The dermis is the layer beneath the epidermis, composed of connective tissue.
• The hypodermis is the layer beneath the dermis, composed of subcutaneous tissue.
• Thin skin is found in areas such as the axilla, while thick skin is found in areas such as the palms and soles.
• The stratum corneum is the outermost layer of the epidermis, composed of dead keratinized cells.
• The stratum lucidum is a layer of the epidermis found in thick skin, composed of dead keratinized cells.
• The stratum granulosum is a layer of the epidermis composed of keratinocytes that are in the process of differentiating.
• The stratum spinosum is a layer of the epidermis composed of keratinocytes that are attached to each other through desmosomes.

Hair Structure

• A hair shaft is the visible part of the hair, while the hair root is the part of the hair that is embedded in the skin.
• The medulla is the innermost layer of the hair shaft, while the cortex is the middle layer.
• The hair bulb is the part of the hair root that is surrounded by the hair follicle.
• The hair papilla is a cluster of blood vessels that supplies the hair follicle with oxygen and nutrients.

Bone Structure

• An osteon is a functional unit of compact bone, composed of concentric lamellae and a central canal.
• The central canal contains blood vessels that supply the bone with oxygen and nutrients.
• Interstitial lamellae are layers of bone tissue that are found between osteons.
• Lacunae are small spaces within the bone tissue that contain osteocytes.
• Canaliculi are small channels that connect lacunae to the central canal.