2022 Anatomy Past Paper PDF

# Introduction to Anatomy of the Human Body ## Table of Contents 1. Introduction to Anatomy of the Human Body 2. The Cell 3. Tissues ## Practice Questions #1: The Cell and Tissues ## Answer Sheet for Practice Questions #1 4. The Integumentary System 5. The Skeletal System I: Skeletal Tissues and...

# Introduction to Anatomy of the Human Body ## Table of Contents 1. Introduction to Anatomy of the Human Body 2. The Cell 3. Tissues ## Practice Questions #1: The Cell and Tissues ## Answer Sheet for Practice Questions #1 4. The Integumentary System 5. The Skeletal System I: Skeletal Tissues and Skeletal Structure 6. The Skeletal System II: The Axial Skeleton 7. The Skeletal System III: The Appendicular Skeleton 8. The Skeletal System IV: Articulations (Joints) ## Practice Questions #2: The Integumentary and Skeletal Systems ## Answer Sheet for Practice Questions #2 9. The Muscular System I: Skeletal Muscle Tissue and Muscle Organization 10. The Muscular System II: Major Muscles of the Axial Skeleton 11. The Muscular System III: Major Muscles of the Appendicular Skeleton ## Practice Questions #3: The Muscular System ## Answer Sheet for Practice Questions #3 12. The Nervous System I: Nervous Tissue 13. The Nervous System II: The Central Nervous System 14. The Nervous System III: The Peripheral Nervous System 15. The Nervous System IV: The Autonomic Division of the Nervous System 16. The Nervous System V: The General and Special Senses 17. The Endocrine System # Chapter 1 - Introduction to Anatomy of the Human Body Anatomy (also called morphology - the science of form) is the study of internal and external structures of the human body. Given that specific structures perform specific functions, therefore, structure determines function. ## The Branches of Anatomy Include: - **Microscopic Anatomy** (fine anatomy) - the study of body structures that cannot be viewed without magnification; includes cytology (the study of cells) and histology (the study of tissues) - **Gross Anatomy** (macroscopic anatomy) - the study of body structures which are visible without the aid of magnification; subclasses include surface anatomy (the study of shapes and markings on the body surface), regional anatomy (the study of all structures in a single body region, superficial or deep) and systemic anatomy (the study of all organs with related functions, i.e. study one organ system at a time) - **Developmental Anatomy** - the study of structural changes that occur from conception to physical maturity; its subclass is embryology (the study of structural formation and development before birth) - **Comparative Anatomy** - the study of the anatomy of different types of animals - **Pathological Anatomy** - the study of structural changes in cells tissues, and organs caused by disease - **Radiographic Anatomy** - the study of internal body structures by using noninvasive imaging techniques, such as X-ray imaging and ultrasound - **Surgical Anatomy** - the study of anatomical landmarks, which are important to surgical procedures ## Levels of Structural Organization of the Human Body (Microscopic to Macroscopic): 1. **Chemical Level:** atoms (building blocks of matter) combine to form small molecules (such as water and carbon dioxide) and larger macromolecules (carbohydrates, lipids, proteins and nucleic acids); i.e., Chemicals (molecules) comprise the entire body. 2. **Cellular Level:** cells are comprised of molecules; they are the smallest living units in the body; cellular organelles are their functional subunits. 3. **Tissue Level:** similar types of cells, with a common function, combine to form tissues; four primary tissue types comprise all organs of the human body. 4. **Organ Level:** more than one tissue type (often all four tissues) combine to form organs; extremely complex physiological processes occur at this level. 5. **Organ System Level:** organs that work closely together combine to form an organ system, to accomplish a common purpose; there are 11 organ systems of the human body. 6. **Human Organism** (or organismal level): the highest level of structural organization; this is the combination of all the organ systems functioning together to sustain the life of the organism. ## The Human Body's 11 Organ Systems: 1. **Integumentary System** - forms the cutaneous membrane (epidermis and dermis), the external body covering; provides protection and thermoregulation; synthesizes vitamin D; provides cutaneous reception through sensory receptors; additional accessory structures are hair follicles, nails, sweat (sudoriferous) glands and oil (sebaceous) glands 2. **Skeletal System** - provides protection and support to the body organs; provides skeletal framework for the muscles to attach, hence, causing movement; stores minerals; blood cell formation occurs within bones 3. **Muscular System** - produces motion; maintains posture by providing support; produces heat 4. **Nervous System** - control center of the body, which directs immediate responses to stimuli and coordinates the other organ systems; i.e. responds to internal and external stimuli by activating appropriate muscles and glands 5. **Endocrine System** - comprised of glands, which secrete hormones that regulate processes (such as metabolism, growth, and reproduction) of the other organ systems 6. **Cardiovascular System** - comprised of the heart, blood vessels, and blood to transport materials (such as respiratory gases, nutrients and wastes) within the body 7. **Lymphoid (Lymphatic and Immune) System** - comprised of the lymphatic vessels, lymphoid organs (lymph nodes, the thymus, and the spleen), lymphocytes, and lymphoid tissue; returns leaked fluid to blood; provides defense against pathogens and disease by housing white bloods cells (lymphocytes) that function in immunity 8. **Respiratory System** - comprised of the nasal cavities, pharynx, larynx, trachea, bronchi, and the lungs; maintains the blood's constant supply of oxygen and removal of carbon dioxide by delivering air to the lungs where gas exchange occurs at the alveoli (air sacs of the lungs) 9. **Digestive System** - comprised of the gastrointestinal tract (or alimentary canal) and accessory structures, which together function to process food and absorb nutrients 10. **Urinary System** - comprised of the kidneys, ureters, the urinary bladder, and the urethra; functions to eliminate excess water, salts, and nitrogenous wastes from the body; regulates water, electrolyte, and acid-base balance of the blood 11. **Reproductive System** - comprised of gonads (testes in the male; ovaries in the female), accessory organs and external genitalia; overall function is to produce sex cells and hormones for the purpose of producing offspring; the female reproductive system supports embryonic development ## Anatomical Positon: Axial vs. Appendicular Regions In anatomical position, the person is standing upright, arms at sides, palms facing forward (little fingers are medial, touching the thighs), feet flat on the floor, face straight ahead. - **The Axial Region** consists of the head, neck and torso. - **The Appendicular Region** consists of the upper and lower limbs (or extremities). ## Orientation and Directional Terms: - **Superior** (cranial or cephalic) – above the point of reference; toward the head end or upper part of a structure or the body - **Inferior** (caudal) - below the point of reference; toward the tail end or toward the lower part of a structure or the body - **Anterior** (ventral) - toward or at the front of the body; in front of; (the front or belly side) - **Posterior** (dorsal) – toward or at the back of the body; behind; (the back side) (n.b. anterior/dorsal and posterior/ventral are interchangeable in humans only, not so in four-footed animals in which dorsal is superior and ventral is inferior) - **Medial** - toward or at the midline of the body; on the inner side of (e.g. The trachea is medial to the arm.) - **Lateral** - away from the midline of the body; toward the sides or on the outer sides of (e.g. The ears are lateral to the nose.) - **Proximal** - closer to the origin of the body part or the point of attachment of a limb to the body trunk (e.g. The shoulders are proximal to the elbows.) - **Distal** - away from the origin of a body part or the point of attachment of a limb to the body trunk (e.g. The fingers are distal to the wrist.) - **Superficial** (external) - closer to or at the body surface (e.g. The skin is superficial to the heart.) - **Deep** (internal) -- farther from or away from the body surface; more internal (e.g. The lungs are deep to the skin.) - **Ipsilateral** - on the same side (e.g. The right arm and right leg are ipsilateral.) - **Contralateral** - on opposite sides (e.g. The right arm and left leg are contralateral.) ## Regional Terms (Names of Specific Body Parts) The following is a list of the most commonly used anatomical terms. | Anatomical Name (Anatomical Region) | Common Term | |:---|:---| | Cephalon (cephalic) | Area of the head | | Cervicis (cervical) | Neck region | | Thoracis (thoracic) | Chest region | | Brachium (brachial) | Upper arm | | Antebrachium (antebrachial) | Forearm | | Carpus (carpal) | Wrist | | Manus (manual) | Hand | | Pollicis (pollex) | Thumb | | Abdomen (abdominal) | Abdominal region | | Umbilicus (umbilical) | Navel or bellybutton | | Pelvis (pelvic) | Pelvic region | | Pubis (pubic) | Anterior pelvis or genital region | | Inguen (inguinal) | Groin | | Lumbus (lumbar) | Lower back | | Gluteus (gluteal) | Buttock region | | Femur (femoral) | Thigh | | Patella (patellar) | Kneecap | | Crus (crural) | Anterior leg, from knee to ankle | | Sura (sural) | Posterior, calf of leg | | Tarsus (tarsal) | Ankle | | Pes (pedal) | Foot (pedals of a bike) | | Planta (plantar) | The bottom of the foot, sole | | Hallucis (hallux) | Great toe or big toe | ## Body Planes - **(a) - Frontal (Coronal) plane** – lies vertically and divides the body into an anterior (front) portion and a posterior (back) portion - **(b) - Transverse (Horizontal) plane** – lies horizontally and divides the body into a superior (top) portion and an inferior (lower) portion. These sections are also called cross sections. - **(c) - Sagittal plane** - lies vertically and divides the body into a right portion and a left portion. If the sagittal plane lies exactly in the midline and the portions are equivalent, it is called a **Midsagittal Plane**, or **Median Plane**; all other sagittal planes (that are offset from the midline and result in unequal portions) are called **Parasagittal Planes**. ## Body Cavities and Membranes 1. **Dorsal body cavity** - **Cranial cavity** - lies within skull (cranium), encasing the brain - **Spinal cavity** - lies within the vertebral column, enclosing the spinal cord 2. **Ventral body cavity (Coelom)** - provides protection, allows organ movement, lining prevents friction - **The Thoracic cavity** - superior to diaphragm, contains heart, lungs, blood vessels; surrounded by the ribs and the muscles of the chest wall - **Pleural Cavities** - right and left cavities, which enclose the right and left lungs - **Parietal pleura** (the thin membrane that lines the chest walls) of the serous membrane - **Visceral pleura** (the thin membrane that adheres to the lungs) of the serous membrane - **Serous fluid** fills the pleural cavity between the layers of the serous membrane - **Mediastinal Cavity or Mediastinum** - a central cavity containing a band of organs, which lies between the pleural cavities; contains the heart (enclosed by the pericardial cavity), esophagus, trachea, and major blood vessels - **Pericardial Cavity** - contains the heart - **Parietal pericardium** (the thin membrane that lines the pericardial walls) of the serous membrane - **Visceral pericardium** (the thin membrane that adheres to the heart surface) of the serous membrane - **Serous fluid** fills the pericardial cavity between the layers of the serous membrane - **The Abdominopelvic Cavity** – lies inferior to the diaphragm and is divided into a superior part and an inferior part - **Abdominal cavity** - the superior part, which contains the liver, stomach, small intestine, spleen, kidneys, and other organs; extends from diaphragm superiorly to superior border of sacrum - **Many organs in the abdominopelvic cavity are surrounded by a peritoneal cavity.** - **Peritoneum** - serous membrane - **Parietal peritoneum** (the thin membrane that lines the wall) of the serous membrane - **Visceral peritoneum** (the thin membrane that adheres to the abdominopelvic organs) of the serous membrane - **Note that the kidneys, adrenal glands, pancreas, and ureters are retroperitoneal because they are located behind the abdominopelvic cavity.** - **Pelvic cavity** - the inferior part, which is enclosed by the bony pelvis; contains the urinary bladder, some reproductive organs, and the rectum - **Peritoneum is continuous with that of the abdominal cavity** ## The four abdominopelvic quadrants (more general method of localizing the visceral organs) delineate the abdominopelvic cavity into four segments by drawing one horizontal plane and one vertical plane through the umbilicus. - **Right upper quadrant (RUQ)** - **Right lower quadrant (RLQ)** - **Left upper quadrant (LUQ)** - **Left lower quadrant (LLQ)** ## The nine abdominopelvic regions (used by clinicians to map the visceral organs) are created by two transverse planes and two parasagittal planes, forming a "tic-tac-toe" grid. - **Umbilical region (5)** -- the center square - **Hypochondriac regions (1-right and 3-left)** -- superior lateral regions - **Epigastric region (2)** -- medial and superior to the umbilical region - **Lumbar regions (4-right and 6-left)** -- middle lateral regions - **Hypogastric region (8)** -- medial and inferior to the umbilical region - **Inguinal (Iliac) regions (7-right and 9-left)** -- inferior lateral regions ## Additional Anatomical and Physiologic Terms: - **Absorption:** the route through which substances (only very small molecules) can enter the body, dependent upon catabolic reactions - **Adaptability:** long-term responsiveness - **Adaptation:** the change in living organisms that allow them to live successfully in an environment - **Differentiation:** the process by which a less specialized cell becomes a more specialized cell type - **Excretion:** the process of removing metabolic waste products and other useless materials - **Growth:** refers to an increase in some quantity over time, often due to an increase in the size and/or number of individual cells - **Metabolism:** the set of chemical reactions that occur in living organisms in order to maintain life - **Anabolism** refers to the construction of molecules, via metabolic pathways, from smaller units. - **Catabolism** refers to the breakdown of molecules, via metabolic pathways, into smaller units, consequently releasing energy. - **Reproduction:** the process through which new individual organisms are produced; therefore, it is essential to the continuity of life. - **Supine:** The patient is lying down with the face up. - **Prone:** The patient is lying down with the face down. - **Responsiveness:** the ability of an organism to change activity or functioning, based upon the application of a stimulus; also referred to as irritability # Chapter 2 - The Cell All living organisms are composed of cells, the basic structural and functional units of life. ## Cell Theory: - Cells are the basic unit of structure in all living things. - New cells are formed/produced from other pre-existing cells, via division. - Cells are the fundamental units of structure that perform all vital functions. ## Two Main Types of Cells in the Body: - **Somatic Cells** - body cells - **Sex Cells** - reproductive cells or germ cells ## Cellular Diversity The trillions of cells in the human body are made up of 200 different cell types that vary greatly in size, shape and function. ## Cytology - **Light Microscopy (LM)** - uses light to magnify and view cellular structures up to 2000x their natural size - **Electron Microscopy (EM)** - uses electrons to magnify and view cell ultrastructures up to 2 million times their natural size ## The 3 Main Parts of the Cell: 1. **Plasmalemma** (plasma or cell membrane) 2. **Cytoplasm** 3. **Nucleus** # Cell Membrane (Plasma Membrane or Plasmalemma) ## Structure - **Fluid Mosaic Model Concept:** - A thin layer of extracellular fluid surrounds a cell. - Its outer boundary is a selectively permeable lipid bilayer called the cell membrane (also called plasma membrane, plasmalemma, or "phospholipids bilayer"). - This cell membrane model is a bilayer of lipid molecules with protein molecules dispersed within it. - **Integral Proteins:** embedded in the phospholipids bilayer - **Peripheral Proteins:** attached to the membrane but can separate from it - **Channels:** allow water and ions to move across the membrane - Gated channels can open and close. - **Microvilli:** tiny fingerlike projections of the cell membrane that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, and cellular adhesion. ## Functions - **Protection:** forms a barrier against substances and forces outside the cell - **Structural Support:** physical interconnections between individual cells occur, as well as connections to their extracellular environment - **Sensitivity:** some membrane proteins act as receptors, a component of the cellular communication system - **Regulation of Exchange with the environment** (i.e., selective permeability): free passage of some (not all) materials are permitted - **Diffusion:** net movement of material from an area of high concentration to an area of low concentration; occurs until equilibrium is achieved (i.e. concentration gradient is eliminated) - **Osmosis:** net movement (or diffusion) of a solvent (frequently water) across a semi-permeable membrane, from a solution of low solute concentration (high water potential) to a solution with high solute concentration (low water potential) - **Facilitated Diffusion** (or facilitated transport): a process of diffusion; a form of passive transport facilitated by the presence of transport (or carrier) proteins - **Active membrane processes** are the mediated processes of moving molecules and other substances across the cell membrane, often requiring energy in the form of ATP (adenosine triphosphate). - **Active Transport:** energy-dependent (require ATP) and independent of concentration gradients; some ion pumps are exchange pumps - **Endocytosis:** a process where cells absorb material (molecules such as proteins) from the outside by engulfing it with their cell membrane. - **Phagocytosis:** cell eating (the process by which cells ingest large objects, such as bacteria or viruses) - **Receptor-Mediated Endocytosis:** a more specific active event where the cytoplasm membrane folds inward to form coated pits - **Pinocytosis:** cell drinking (uptake of solutes and single molecules, such as proteins) ## The Cytoplasm Consists of three major elements: cytoplasm, organelles, and inclusions. - **Cytosol** - an intracellular fluid that contains dissolved solutes, and surrounds the cellular organelles - **Organelles** - specialized subunits within a cell that has specific functions ## Membranous Organelles: Separately enclosed within their own lipid membranes that isolate them from the cytosol 1. **The Nucleus** - contains the cell's chromosomal DNA - Surrounded by the **Nuclear Envelope** (double-layered membrane) - Contains the fluid **Nucleoplasm** - Contains **Nucleoli** (the site of ribosomal RNA synthesis; singular-nucleolus) - Contains **Chromatin** (chromosome in the non-coiled state when the cell is not dividing) - Functions as the **control center of the cell** - Its genetic material, DNA, directs the cell's activities by providing the instructions for protein synthesis - Also responsible for transmitting genetic information 2. **Mitochondrion** (plural = mitochondria) - bean-shaped organelles, which are described as "cellular power plants" because they generate most of the cell's supply of ATP (95% of the supply), used as a source of energy - Consists of two membranes: - The **outer mitochondrial membrane**, which encloses the entire organelle and - The **inner mitochondrial membrane** that folds inward to produce **Cristae**, which increase the surface area and enhance the organelle's ability to produce ATP - **Mitochondrial Matrix** - the space enclosed by the inner membrane - Important in the production of ATP with the aid of the ATP synthase contained in the inner membrane 3. **Endoplasmic Reticulum (ER)** - an interconnected network of tubules, vesicles and cisternae (rounded chambers), which is involved in synthesis, storage, transport, and detoxification - **Rough ER (RER)** has attached ribosomes, where proteins are assembled and packaged in transport vesicles to be exported to the Golgi apparatus. The rough ER has several functions in making all proteins that are secreted from cells, on its ribosomes, and providing RER membrane for the cell membrane. - **Smooth ER (SER)** does not have attached ribosomes. It functions in lipid and carbohydrate (steroid) synthesis, lipid metabolism, calcium ion storage, and drug detoxification. 4. **Golgi Apparatus** (also called the Golgi body, Golgi complex, or dictyosome) - composed of flattened membrane-bound stacks known as cisternae (singular = cisterna) - Functions in packaging materials for lysosomes, peroxisomes, secretory vesicles, and membrane segments that are used to replenish the cell membrane - Transport vesicles from the RER are processed from the cis-Golgi (convex end) to trans-Golgi (concave end) through the apparatus. - Secretory products are discharged from the cell through the process of exocytosis (the ejection of cytoplasmic materials by fusion of a membranous vesicle with the cell membrane) 5. **Lysosomes** - spherical, membrane-walled sacs that contain digestive enzymes (acid hydrolases) - Function in digesting unwanted substances, such as excess or worn-out organelles, food particles, and engulfed viruses or bacteria 6. **Peroxisomes** - smaller, membrane-walled sacs that contain enzymes, especially oxidases and catalases, that function in removing toxic peroxides from the body - **Peroxide:** a compound that contains an oxygen-oxygen single bond ## Non-Membranous Organelles: Not enclosed within their own lipid membranes; hence, they are always exposed to the cytosol 1. **Ribosomes** - complexes of two subunits (ribosomal RNA and protein); function as the site of protein synthesis; two types found in cells - **Free ribosomes** - located within the cytosol - **Fixed ribosomes** - bound to the ER 2. **Cytoskeleton** - an elaborate, internal network of protein rods spanning throughout the cytosol; confers strength and flexibility to the cytoplasm; provides support and shape to the cell, as well as intracellular movement - **Microtubules** - composed of the protein tubulin; function as the main support of the cell; allow the cell to change shape; allow organelle movement; function during cell division in moving and separating DNA strands - **Microfilaments** - mainly composed of thin strands of the actin protein - **Intermediate Filaments** - function in providing strength, stabilization of the organelles, and transport of materials within the cytoplasm - **Thick Filaments** - mainly composed of the protein myosin; produce movement with the action of actin 3. **Centrioles** - long, barrel-shaped microtubules that radiate from the centrosome (spherical structure in the cytoplasm near the nucleus) in non-dividing cells. - Active in dividing cells and function in directing the movement of chromosomes during cell division - Also function in forming the bases of cilia and flagella 4. **Cilia** (sing. = cilium) - microtubules containing tail-like projections that are anchored by a basal body - Function in movement of fluids or secretions across the cell surface, by beating rhythmically 5. **Flagellum** (pl. = flagella) - a whip like projection that functions in moving a cell through surrounding fluid - This is a longer version of the cilium; found only on sperm, enabling them to swim in the female reproductive tract. 6. **Microvilli** (sing. = microvillus) - tiny fingerlike projections of the cell membrane that increase the surface area of cells ## Inclusions - Chemical substances in the cytoplasm that may or may not be present in a cell, depending on the cell type - These are often stored nutrients, secretory products, and pigment granules ## Intercellular Attachments: There are three different types of cell junctions, by which cells attach to each other or to extracellular protein fibers. 1. **Occluding Junction** (or **Tight junction**) - the lipid portions of the plasma membranes bind together to seal the intercellular space between the cells, thereby preventing materials from passing between them 2. **Communicating Junction** (or **Gap junction**) - membrane or channel proteins, called connexons hold two cells together, forming a narrow passageway (channels) between the cells 3. **Anchoring Junction** --- two adjacent cells are mechanically linked together at their lateral or basal surfaces - **Desmosome** (also called macula adherens or macula adherents) - a system of cell adhesion molecules (CAMs = large transmembrane proteins that bind cells to each other and to the extracellular fluid) and intercellular cement that glue adjacent cells together - **Hemidesmosome** - a very small stud- or rivet-like structure on the inner basal surface that attaches a cell to the filaments and fibers of the extracellular matrix ## The Cell Life Cycle - **Cell Division:** the series of events that take place in an eukaryotic (nucleated) cell, leading to its replication; divided into two brief stages - **Interphase** is divided into the G1, S, G2 Stages - **G1:** cells are metabolically active, make proteins rapidly, and grow vigorously - **S:** DNA replicates itself - **G2:** final part of interphase where enzymes needed for cell division are synthesized - **M Phase**, or mitotic phase (cells divide in this phase) composed of two tightly-coupled processes: - **Mitosis** (or mitosis proper) and **Cytokinesis**, which together define the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell ## The Stages of Mitosis (Mitosis Proper) in Chronological Order Are: - Prophase, Metaphase, Anaphase, and Telophase. ## Mnemonic Devices: - "PMAT" or "Please Make A Taco" = Prophase, Metaphase, Anaphase, Telophase - Another mnemonic device for memorizing the stages of mitosis including interphase and cytokinesis is "I Party More At The Club," or "IPMATC." - Another way of remembering it is: "In Paris Many Artists Teach" = Interphase, Prophase, Metaphase, Anaphase, and Telophase. ## Major Events in the Stages of Mitosis Proper ("PMAT") and Cytokinesis: 1. **Prophase** - The chromatin threads coil and condense, forming barlike chromosomes, each of which are comprised of two identical chromatin threads, now called chromatids. - Chromatids are held together by a small, buttonlike body called a centromere and cohesin (a protein complex). - Nucleoli disappear as chromosomes appear. - Cytoskeletal microtubules disassemble. - The mitotic spindle (a new assembly of microtubules) forms between the centriole pairs. - The nuclear envelope fragments and begins to be dispersed to the ER. 2. **Metaphase** - Chromosomes cluster at the middle of the cell - Centromeres precisely align at the equator (exact center) of the spindle, at the metaphase plate. - *Memory aid: "M" is for "Metaphase" and chromosomes align in the "middle" of the dividing cell* 3. **Anaphase:** shortest stage of mitosis; typically lasts only a few minutes - Begins abruptly as the **chromatid pairs separate** (centromeres of the chromosomes split), and each chromatid now becomes a chromosome in its own right. - The **V-shaped daughter chromosomes** move toward opposite ends of the cell. - *Memory aid: The **V-shaped chromosomes** also look like the letter "A" without the horizontal line; hence, **"A"-shaped chromosomes** could be associated with the "Anaphase" stage* 4. **Telophase** - Begins as soon as chromosomal movement stops - Nuclear membranes form and the nuclei enlarge as the chromosomes begin to uncoil. - Nucleoli reappear and the nuclei resemble those of interphase cells. - *Memory aid: This final phase is like prophase in reverse.* 5. **Cytokinesis** completes the division of the cell into two daughter cells - Occurs as a contractile ring of peripheral microfilaments forms at the cleavage furrow and squeezes the cells apart - Actually begins during late anaphase and continues through and beyond telophase # Chapter 3 - Tissues ## Introduction - Tissues are groups of closely associated specialized cells, which are similar in structure, and perform related (and limited) functions. - Histology is the study of tissues. ## Four Primary Tissue Types: - Epithelial tissue (epithelium) - Connective tissue - Muscle tissue - Nervous (neural) tissue # Epithelium (Singular) / Epithelia (Plural) Epithelium is a sheet of cells that covers a body surface or lines a body cavity. ## Functions: - Protection - Sensory reception - Secretion - Absorption - Ion transport ## Special Characteristics: 1. **Cellularity** - epithelia is composed of abundant densely-packed cells and very little extracellular material 2. **Specialized contacts** such as cell junctions 3. **Polarity:** apical and basal regions exist and differ in structure and function 4. **Support by underlying connective tissues** 5. **Avascular but innervated** 5. **Regeneration:** due to high mitotic rates and the presence of mesenchymal (stem) cells, epithelia can regenerate. ## Epithelial Surface Features: ### Apical Surface Features: - **Microvilli** - increase epithelial surface area; may anchor sheets of mucus - **Stereocilia** - very long microvilli that cannot move - **Cilia** - move fluid, usually mucus ### Lateral Surface Features: - **Cell junctions** - desmosomes, tight junction, gap junction ### Basal Surface Features: - **Basal lamina** - a sheet of proteins, which acts as a filter and as a scaffolding on which regenerating epithelial cells grow - **Basement membrane** - formed by the basal lamina plus some underlying reticular fibers ## Classification of Epithelia ### Based on Number of Cell Layers: - **Simple** (one layer of cells) - **Stratified** (2 or more layers of cells) - the superficial or apical layer is used to classify the epithelial type - **Pseudostratified with cilia** - a simple epithelium that contains both short and tall cells; classification used mainly in one type (pseudostratified columnar) ### Based on Cell Shape: - **Squamous** (flattened cytoplasm and nucleus) - **Cuboidal** (spherical nucleus) - **Columnar** (oval or elongated nucleus, usually located basally) - **Transitional epithelia** are a stratified epithelium that stretches and changes shape due to the expansion of their cells' lumens (open spaces) ## Epithelial Tissues - **Simple Squamous Epithelium** - lines alveoli of the lungs (Refer to "Based on cell shape" sample diagram for visual reference) - Forms the endothelium of blood vessels and the mesothelium of the ventral body cavity - Molecules rapidly diffuse (passive) through the delicate and thin layer of flat cells of this epithelium - **Stratified Squamous Epithelium** (Figure 15B below) - non-keratinized type forms the moist linings of the esophagus, mouth, and vagina - **Keratinized type** forms the epidermis of the skin - Protects underlying tissues in areas subjected to abrasion - **Simple Cuboidal Epithelium** occurs in kidney tubules and in ducts and secretory portions of small glands (Refer to "Based on cell shape" sample diagram for visual reference) - Functions in secretion and absorption - **Stratified Cuboidal Epithelium** - occurs in largest ducts of sweat glands, mammary glands, and salivary glands - Functions in protection - **Simple Columnar Epithelium** - non-ciliated type lines the stomach and intestines, gallbladder, and excretory ducts of some glands (Refer to "Based on cell shape" sample diagram for visual reference) - **Ciliated type** lines small bronchi, uterine tubes and some regions of the uterus - Functions in absorption, secretion, and ion transport - **Stratified Columnar Epithelium** - rare existence in the body - Small amounts occur in the male urethra and in large ducts of some glands - Functions in protection and secretion - **Pseudostratified (Ciliated) Columnar Epithelium** (Figure 15A below) – non-ciliated type lines the sperm-carrying ducts and ducts of large glands - **Ciliated variety** lines the trachea and most of the upper respiratory tract - Function in secretion (especially mucus) and propulsion of mucus by ciliary action - **Transitional Epithelium** (Figure 15C below) – lines the ureters, bladder, and part of the urethra - Stretches readily and permits distension of urinary organ by contained urine ## Glands - Many epithelial cells make and secrete a product (aqueous fluid containing proteins usually); such cells constitute glands - **Exocrine glands** secrete their products onto body surfaces (skin) or into body cavities - **Contain ducts** that carry secreted products to epithelial surface - **Serous glands** produce a watery solution that usually contains enzymes. - **Mucous glands** produce viscous, sticky mucus. - **Mixed glands** produce both types of secretions. - **Unicellular glands (Goblet Cells)** are the individual secretory cells that occur in epithelia containing scattered gland cells. - **Multicellular glands** occur as aggregations of gland cells (glandular epithelia) that produce exocrine or endocrine secretions. - **Classified** by their ducts (simple or compound) and by the structure of their secretory units (tubular, alveolar or acinar, or tubuloalveolar) ## Mechanisms of Secretion - **Apocrine secretion** - a portion of the secreting cell's body is lost during secretion (e.g. lactiferous glands in the breast) - **Holocrine secretion** - the entire cell disintegrates to secrete its substances (e.g. sebaceous glands) - **Merocrine (Eccrine) secretion** - cells secrete their substances by exocytosis (e.g. mucous and serous glands) - **Endocrine glands** are ductless and secrete product (usually hormones) directly into the bloodstream. # Connective Tissue - the most diverse and abundant tissue type ## Four Classes: - Connective tissue proper - Cartilage - Osseous (bone) tissue - Blood ## Common embryonic origin is mesenchyme. ## Structure: - Cells separated from one another by a large amount of extracellular matrix (ground substance + fibers + tissue fluid) - **The structure of blood is an exception in this case.** ## Connective Tissue Proper - **Fibroblast** - the most abundant cell type in connective tissue proper - **Produces** both the fibers and the ground substance of the extracellular matrix - **Three types of fibers in connective tissues** - **Collagen fibers** - resist tension - **Reticular fibers** - provide structural support - **Elastic fibers** - enable recoil of stretched tissues - **Loose (Areolar / Adipose / Reticular) Connective Tissue Proper:** - **Areolar** - underlies almost all epithelia and surrounds capillaries - Ground substance and collagen, reticular and elastic fibers in the matrix surround fibroblast cells, fat (adipose) cells and defense cells. - **Adipose** - similar to areolar but contains more adipose cells. - Functions in increased nutrient-storage - **White fat** is