Anatomy & Physiology: Cell Structure, Epithelial Tissue, and Skeletal System Study Guide

Cell Structure

Major Organelles of the Eukaryotic Cell

The eukaryotic cell contains various organelles, each with specialized functions essential for cell survival and activity. Understanding their structure and function is fundamental in anatomy and physiology.

• Cell Membrane (Plasma Membrane): The outer boundary of the cell, composed of a phospholipid bilayer with embedded proteins. It regulates the movement of substances in and out of the cell and provides protection and structural support.

• Nucleus: The control center of the cell, containing genetic material (DNA). It directs cellular activities such as growth, metabolism, and reproduction.

• Nucleolus: Located within the nucleus, it is responsible for ribosome synthesis.

• Ribosomes: Small structures either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum; they are the sites of protein synthesis.

• Rough Endoplasmic Reticulum (RER): Studded with ribosomes, it is involved in protein synthesis and modification.

• Smooth Endoplasmic Reticulum (SER): Lacks ribosomes and is involved in lipid synthesis and detoxification processes.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Mitochondria: The "powerhouse" of the cell, responsible for producing ATP through cellular respiration.

• Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris.

• Centrioles: Involved in organizing microtubules during cell division.

• Cytoplasm: The jelly-like substance that fills the cell and surrounds the organelles.

Example: The mitochondria generate ATP, which is used as an energy source for cellular processes such as muscle contraction and nerve impulse transmission.

Epithelial Tissue

Classification of Epithelial Tissue

Epithelial tissue covers body surfaces, lines cavities, and forms glands. It is classified based on the arrangement of layers and the shape of the cells.

• Arrangement of Layers:

  • Simple Epithelium: Single layer of cells; functions in absorption, secretion, and filtration.

  • Stratified Epithelium: Multiple layers of cells; provides protection against abrasion.

  • Pseudostratified Epithelium: Appears to have multiple layers due to cell nuclei at different levels, but all cells rest on the basement membrane.

• Cell Shape:

  • Squamous: Flat and thin cells; allow for rapid diffusion (e.g., alveoli of lungs).

  • Cuboidal: Cube-shaped cells; involved in secretion and absorption (e.g., kidney tubules).

  • Columnar: Tall, column-like cells; specialized for absorption and secretion (e.g., lining of the intestines).

Example: The simple squamous epithelium lines blood vessels and facilitates the exchange of gases and nutrients.

Skeletal System: Skull Anatomy

Major Bones of the Skull

The human skull is composed of several bones that protect the brain and form the structure of the face. Understanding the location and function of these bones is essential in anatomy.

• Frontal Bone: Forms the forehead and the upper part of the eye sockets.

• Parietal Bones: Paired bones forming the sides and roof of the cranial cavity.

• Temporal Bones: Located at the sides and base of the skull; house the structures of the ears.

• Occipital Bone: Forms the back and base of the skull; contains the foramen magnum.

• Sphenoid Bone: Located at the base of the skull, in front of the temporals.

• Ethmoid Bone: Forms part of the nasal cavity and the orbits.

• Zygomatic Bones: Cheekbones; form part of the orbit.

• Maxilla: Upper jawbone; forms part of the orbit, nose, and palate.

• Mandible: Lower jawbone; the only movable bone of the skull.

Example: The mandible is essential for mastication (chewing) and forms the lower jawline.

Short Answer and Concept Review Topics

Key Concepts in Anatomy & Physiology

The following are important topics and questions for review in anatomy and physiology, focusing on tissues, bones, and cellular functions.

• Axial vs. Appendicular Skeleton: The axial skeleton includes the skull, vertebral column, and rib cage; the appendicular skeleton includes the limbs and girdles.

• Epiphysis and Endosteum: The epiphysis is the end part of a long bone; the endosteum is a thin membrane lining the medullary cavity.

• Cell Types and Functions: Epithelial cells cover surfaces; microvilli increase surface area for absorption; goblet cells secrete mucus.

• Transitional Epithelium: Specialized to stretch and found in the urinary bladder.

• Endocrine vs. Exocrine Glands: Endocrine glands secrete hormones into the bloodstream; exocrine glands secrete substances through ducts.

• Fibroblasts and Collagen: Fibroblasts produce collagen, a strong protein fiber found in connective tissue.

• Adipose, Chondrocytes, Osteocytes: Adipose cells store fat; chondrocytes are found in cartilage; osteocytes are mature bone cells.

• Neurons and Neuroglia: Neurons transmit nerve impulses; neuroglia support and protect neurons.

• Spongy vs. Compact Bone: Spongy bone is porous and found at the ends of long bones; compact bone is dense and forms the outer layer of bones.

• Serous and Mucous Membranes: Serous membranes line body cavities and secrete serous fluid; mucous membranes line cavities open to the exterior and secrete mucus.

Example: The thoracic spine is part of the axial skeleton and provides attachment points for the ribs.

Table: Comparison of Epithelial Tissue Types

Type	Layers	Shape	Main Function	Location Example
Simple Squamous	1	Flat	Diffusion, filtration	Alveoli, blood vessels
Simple Cuboidal	1	Cube-shaped	Secretion, absorption	Kidney tubules
Simple Columnar	1	Tall, column-like	Absorption, secretion	Digestive tract lining
Stratified Squamous	Multiple	Flat	Protection	Skin, mouth lining
Transitional	Multiple	Variable	Stretching	Urinary bladder

Key Formulas and Terms

• ATP Production (Cellular Respiration):

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP$

• Osteon (Haversian System): The structural unit of compact bone.

• Microvilli: Increase surface area for absorption, especially in the small intestine.

Additional info: Some content and terminology were inferred and expanded for academic completeness based on standard Anatomy & Physiology curricula.