Cellular Structure, Tissues, and Skeletal System

• Study notes on cellular structure, reproduction, tissues, and the skeletal system are outlined below

Cellular Structure

• The plasma membrane is a phospholipid bilayer containing proteins and cholesterol
• The plasma membrane is responsible for: transport, receptor communication, cell-cell binding, and self-recognition
• The endoplasmic reticulum (ER) includes the Rough ER (RER) and Smooth ER (SER)
• The Rough ER (RER) is studded with ribosomes for protein synthesis
• The Smooth ER (SER) is responsible for lipid synthesis, calcium storage, and detoxification
• Ribosomes synthesize proteins and are free in the cytoplasm (for internal use) or on the RER (for export)
• The Golgi apparatus processes, modifies, and transports proteins and produces vesicles for secretion
• Lysosomes contain digestive enzymes that break down waste and defective organelles
• Proteasomes degrade proteins, which is important for removing defective proteins
• Mitochondria are the powerhouse of the cell that produce ATP
• Mitochondria have their own DNA
• The nucleus contains DNA and each nucleolus produces rRNA for ribosomes
• The nuclear envelope controls the exchange between the nucleus and cytoplasm
• The cytoskeleton includes microfilaments, intermediate filaments, and microtubules, it is important for structure and movement

Cellular Reproduction

• The cell cycle phases are: G1, S, G2, M, and G0
• During the G1 phase, the cell grows and prepares for DNA synthesis
• During the S phase, DNA replication occurs
• During the G2 phase, the cell prepares for mitosis
• During the M phase, mitosis (cell division) occurs
• During the G0 phase, the cell is in a resting phase (non-dividing cells)
• Mitosis phases are: prophase, metaphase, anaphase, and telophase
• During prophase, chromatin condenses, the nuclear envelope dissolves, and the spindle forms
• During metaphase, chromosomes align at the equator
• During anaphase, sister chromatids separate and move to opposite poles
• During telophase, the nuclear envelope reforms, chromosomes decondense, and cytokinesis completes
• Meiosis includes two divisions that create gametes (sperm & ova) with half the chromosome number (haploid)
• Meiosis increases genetic variability through crossing-over and independent assortment

Tissues

• The four types of tissues are: epithelial, connective, muscle, and nervous
• Epithelial tissue covers body surfaces and lines cavities and is responsible for secretion, absorption, and protection
• Connective tissue supports, connects, and transports, where cells are spread out in the ECM
• Muscle tissue produces movement, including skeletal, smooth, and cardiac types
• Nervous tissue facilitates communication and control, with neurons and neuroglia
• Epithelial tissue is classified as simple (one layer) or stratified (multiple layers)
• Epithelial tissue: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall), Pseudostratified, Transitional
• Epithelial tissues provide protection, secretion, absorption, and excretion
• Connective tissues include loose (under skin), dense (tendons, ligaments), cartilage (hyaline, fibrocartilage, elastic), bone, and blood
• Muscle tissues include skeletal (voluntary, striated), smooth (involuntary, non-striated), and cardiac (involuntary, striated, with intercalated discs)
• Nervous tissue contains neurons (transmit signals) and neuroglia (support cells)
• Tissue repair occurs via either regeneration (epithelial & connective) or scarring (fibrous tissue)

Skeletal System

• Bone structure includes compact bone (osteons, Haversian canals) and spongy bone
• The periosteum is the outer membrane with osteoblasts (build bone)
• Bone cells include osteoblasts (build bone), osteoclasts (break down bone), and osteocytes (mature bone cells in lacunae, connected by canaliculi)
• Parathyroid hormone (PTH) increases blood calcium by stimulating osteoclasts
• Calcitonin decreases blood calcium by stimulating osteoblasts
• Bone functions include protection, movement, mineral storage, and blood cell formation
• The three types of joints are: synovial (freely movable), cartilaginous (slightly movable), and fibrous (immovable)
• Body movements include flexion, extension, abduction, adduction, rotation, and circumduction
• Disorders of the skeletal system include osteogenesis imperfecta (brittle bones), osteoporosis (bone thinning), and arthritis (joint inflammation)