Lecture 5: Human Body PDF

Overvieuw : - From cells to organ systems - Tissues - Epithelial, Connective, Nervous, Muscular - Organ systems: - Skeletal, Muscular, Circulatory, Respiratory, Lymphatic, Nervous, Endocrine, Digestive, Urinary, Reproductive, Integumentary - Main components and functions From...

Overvieuw : - From cells to organ systems - Tissues - Epithelial, Connective, Nervous, Muscular - Organ systems: - Skeletal, Muscular, Circulatory, Respiratory, Lymphatic, Nervous, Endocrine, Digestive, Urinary, Reproductive, Integumentary - Main components and functions From cells to organs: --------------------- **From cell to organ systems:** - Humans have systems of organs that work together, carrying out processes that keep us alive - The body has levels of organization that build on each other: cells make up tissues à tissues make up organs à organs make up organ systems - The function of an organ system depends on the integrated activity of its organs - The survival of the organism depends on the integrated activity of all the organ systems coordinated by the endocrine and nervous systems **From a cell to a human:** Example: - For a single-cell organism in a nutrient place, staying alive is pretty straightforward! - absorbs nutrients straight from the environment - oxygen needed for metabolism can diffuse in across the cell membrane - carbon dioxide and other wastes can diffuse out - when the time comes to reproduce, it can just divide in two **Organ systems:** For us its more complicated, we are composed of different organ systems that work together in a cooperate manner: Systems of protection, support & movement - Skeletal system - Muscular system - Integumentary system Systems of internal communication & integration - Nervous system - Endocrine system Systems of fluid transport - Circulatory system - Lymphatic system Systems of intake & output - Respiratory system - Urinary system - Digestive system Systems of reproduction - Male/female reproductive system Tissues ------- **Histology: tissue** Histology: the study of tissues and the way they are arranged into organs Tissue: a group of similar cells and cell products that arise from the same region of an embryo and work together to perform a specific structural or physiological role in an organ The Four Primary Tissue Classes: - Epithelial - Connective - Nervous - Muscular **Epitheal:** - Epithelial: Tissue composed of layers of closely spaced cells, covers organ surfaces, forms glands, and serves for protection, secretion, and absorption (e.g. epidermis, lining of digestive tract, liver, and other glands) - Types of epithelial tissue: flat cells or squamous cells; cube-shaped cells or cuboidal cells; tall and cylindrical ones or columnar cells - Layers of epithelial tissue: - simple epithelium has a single layer sheet of cells - two or more layers is the stratified epithelium - pseudostratified epithelium appears to have more than one layer but is a single sheet of different height cells - transitional epithelium where the cells change shape in response to mechanical stretching  **Connective:** - Cells embedded within a network of fibers: the matrix - Material surrounding the cells within the matrix: the ground substance - Connective: Tissue with usually more matrix than cell volume, often specialized to support, bind, and protect organs (e.g. tendons, ligaments, cartilage, fat, bone, blood) - Types based on characteristics of matrix and ground substance: - connective tissue proper containing various fibers in a semifluid ground substance - bone tissue that has a fibrous matrix but exceptionally solid ground substance, the bone - blood that has fluid ground substance and no solid matrix except after clotting - cartilage tissue has solid ground substance, the cartilage that has a fibrous matrix (no blood vessels, in most places replaced by bone) **Nervous:** Nervous: Tissue containing excitable cells specialized for rapid transmission of information to other cells (e.g. brain, spinal cord, nerves)  **Muscular tissue:** Muscular: Tissue composed of elongated, excitable cells specialized for contraction and movement (e.g. skeletal muscles; heart; walls of uterus, bladder, intestines)  Red= skeletal muscles Clear = Adipus/ fat tissue Purple= connective tissue Organ systems: -------------- **Skeletal system:** - The skeletal system is composed of bones, cartilage, and ligaments joined tightly to form a strong, flexible framework for the body - Joint: a bone meets another bone - Cartilage: forerunner of most bones in embryonic development, it forms a growth zone in the bones of children, and it covers many joint surfaces in the mature skeleton - Ligaments: collagenous bands that hold bones together at the joints (joints: 2\ bones meet) - Tendons: structurally similar to ligaments but attach muscle to bone bone marrow: the soft bloody or fatty material enclosed in the bones - Support: bones of the limbs and vertebral column support the body, the mandible and maxilla support the teeth, and some viscera are supported by nearby bones - Protection: bones enclose and protect the brain, spinal cord, lungs, heart, and pelvic viscera - Movement: bones provide attachment and leverage for the muscular system, allowing for such actions as limb movement and ventilation of the lungs - Blood formation: red bone marrow is the major producer of blood cells - Storage: the skeleton is the body's main reservoir of calcium and phosphorus, among other minerals There are 109 differently named bones of the skeleton (most paired) an adult skeleton typically has 206 individual bones. These are divided into two regions: axial and appendicular The axial skeleton forms the central supporting axis of the body and comprises 80 bones: including the skull, vertebral column, ribs and sternum. The appendicular skeleton comprises the remaining 126 bones, those of the upper limb and pectoral girdle, and of the lower limb and pelvic girdle. **The muscular system:** - There are three types of muscular tissue: skeletal, cardiac, and smooth. When we talk about the muscular system we talk about the skeletal type of muscular tissue. This means that we are talking about the muscles that we can voluntarily move. **Functions:** - Movement - Stability - Control of body openings and passages - Heat generation - Glycemic control **Structure of the Muscle Fiber:** - Skeletal muscle cells are called muscle fibers - Each muscle fiber has multiple nuclei pressed against the plasma membrane - deeper part of the cell: thick bundles (myofibrils) of contractile protein (myofilaments: actin and myosin) - Packed between myofibrils are numerous mitochondria, a network of smooth endoplasmic reticulum, deposits of the high-energy carbohydrate glycogen, and a red oxygen-binding pigment, myoglobin **The muscular system: cardiac muscle** - Cardiac muscle is limited to the heart, where its function is to pump blood Properties: - involuntary (contracts automatically) and autorhythmic (has a self-maintained - rhythm of contraction) à The rhythm is set by a pacemaker in the wall of the upper heart - Cardiac muscle cells are short, rectangular and forked at the ends linked at the intercalated discs - Each heart chamber sustains its contraction (250 ms) long enough to effectively expel blood - Cardiac muscle is very rich in myoglobin and glycogen and has especially large mitochondria **The muscular system: smooth muscle** - Smooth muscle is involuntary, like cardiac. But, it lacks striations: this is why it is called smooth - Smooth muscle cells have only one nucleus near the middle of the cell, are - fusiform in shape - Smooth muscle occurs in the walls of the blood vessels and many body-cavity - organs (viscera), such as the respiratory, urinary, digestive, and reproductive - organs: called visceral muscle - Smooth muscle contracts in response to nervous stimulation, stretch (as in a full - bladder), hormones (during labor contractions), and blood levels of CO2 , O2 and pH - Smooth muscle is fully capable of mitosis (e.g., pregnant uterus) Age and muscles the muscular system. The more you exercise the less adipus tissue you have and the more your muscles are intact. **Circulatory systems:** - A circulatory system has three basic components: - a circulatory fluid - a set of interconnecting vessels - a muscular pump, the heart The heart powers circulation by using metabolic energy to elevate the circulatory fluid's hydrostatic pressure The fluid then flows through the vessels and back to the heart - In mammals: - O2 from inhaled air diffuses across only two layers of cells in the lungs before reaching the blood - The circulatory system then carries the oxygen-rich blood to all parts of the body - As the blood passes throughout the body tissues in tiny blood vessels: O2 in the blood diffuses only a short distance before entering the fluid that directly bathes the cells The heart: - The heart has four chambers that receive and eject blood - The two smaller, superior chambers are the right and left atria They are thin- walled receiving chambers for blood returning to the heart by way of the great veins - The two inferior chambers, the right and left ventricles compose most of the bulk of the heart à They are strong pumps that eject blood into the arteries and keep it flowing around the body Heart's valves: - Four heart valves ensure a one-way flow of blood and prevent backflow of blood: - one between each atrium and its ventricle and one at the exit from each ventricle to its great artery - The atrioventricular (AV) valves control the opening between each atrium and\ the ventricle below it - The pulmonary and aortic valves (collectively called semilunar valves) lie\ between the ventricles and great arteries - The pulmonary valve controls the opening from the right ventricle into the\ pulmonary trunk - The aortic valve controls the opening from the left ventricle into the aorta The Pulmonary and Systemic Circuits: - The cardiovascular system has two major divisions: - Pulmonary circuit: carries blood to the lungs for gas exchange and returns it to the heart, and - Systemic circuit: supplies blood to all organs of the body, including the lungs and the wall of the heart itself à It pumps blood into the largest artery, the aorta - The dual circuits operate simultaneously - The two ventricles contract almost in unison and pump the same volume of blood - The total volume of the systemic circuit is much greater than that of the pulmonary circuit Blood Vessels: - Three categories of blood vessels: arteries, veins, and capillaries. They differ in: - direction of blood flow - pressure they withstand - corresponding histological structure of their walls - All vessels that carry blood away from the heart are classified as arteries - All vessels that carry blood back to the heart are classified as veins - Capillaries are microscopic vessels connecting the smallest arteries to the smallest veins. **Respiratory system:** Respiratory functions: - Gas exchange: oxygen enters blood and carbon dioxide leaves - Regulation of blood pH: altered by changing blood carbon dioxide levels - Voice production: movement of air past vocal folds makes sound and speech - Olfaction: smell occurs when airborne molecules drawn into nasal cavity - Protection: against microorganisms by preventing entry and removing them Respiratory tract: - Air passages from the nose to the lungs and gas-exchange surfaces in the lungs themselves - Upper respiratory tract: from nose through larynx - Lower respiratory tract: from trachea through lungs The bronchial tree and alveoli - a series of branching passages that carry air from trachea to gas-exchange surfaces in the lungs (alveoli) - bronchi branch into smaller passageways leading to tubes called bronchioles and terminal bronchioles - Each lung contains 150 million alveoli, which provide a large surface area for gas exchange Respiratory cycle: - Breathing (pulmonary ventilation): inspiration (inhaling) and expiration (exhaling) - One complete inspiration and expiration is called a respiratory cycle - Inhalation/ inspiration: main organ participating is diaphragm. When we inspire the diaphragm and other make the space as large as possible so air has space. Diaphragm goes down and everything else goes up. Muscle conscript and ribcage expands. - Expiration: passive process, everything goes back, diaphragm goes up and everything goes down and relaxes. **Lymphatic system:** - Defense against pathogens (bacteria, viruses, fungi etc): the lymphatic system - A network of tissues, organs, and vessels: recover tissue fluid, inspect and cleanse it of pathogens, activate immune responses, and return the fluid to the bloodstream Components: 1. Lymph: fluid that the system collects from the tissues and returns to the bloodstream 2. Lymphatic vessels: resemble veins and transport the lymph 3. Lymphatic tissue: loose aggregations of lymphocytes in the connective tissues of various organs such as the digestive and respiratory tracts 4. Lymphatic organs: structures enclosed in a fibrous capsule and containing organized masses of lymphatic tissue (e.g. tonsils, thymus, spleen, and lymph nodes) - The principal lymphatic organs are the tonsils, thymus, spleen and lymph nodes - Lymph nodes: small lumps of tissue that contain white blood cells (mainly B and T lymphocytes) Functions 1. Fluid recovery: Fluid continually seeps from the blood capillaries into tissue spaces à blood capillaries reabsorb 85% of this fluid and lymphatic system absorbs 15% (2-4 L/day) 2. Immunity: Fluid recovered from body tissues is checked by the lymphatic system for toxins, microbes, it guards the openings of the digestive, respiratory, and other tracts 3. Lipid absorption: lymphatic vessels 'lacteals' in the small intestine absorb dietary lipids à through lymphatic vessels lipids empty into large left subclavian vein à from here, bloodstream distributes them for storage or immediate use **The nervous system:** **Functions:** 1. Sensory: the ability to respond to stimuli within and around the body, and generate signals that carry information about stimuli to spinal cord or brain 2. Integrative: the ability to receive and process information, store and retrieve it, and make decisions as to whether or how to respond to it 3. Motor: the ability to issue outgoing signals to muscle and gland cells to produce a response Two main anatomical subdivisions: 1. The central nervous system (CNS): brain and spinal cord (enclosed and protected by cranium and vertebral column) It carries out the integrative functions of the nervous system. 2. The peripheral nervous system (PNS): nerves leading to and from the CNS It provides the CNS with pathways of signal input and output, connecting it to the body's sense organs, muscles, and glands It carries out both sensory and motor functions **The neuron:** - soma or cell body: the control center of neuron Nucleus: the cell's site of genetic control - Dendrites: the ''receiving end" of a neuron (from other neurons) - Axon (nerve fiber): the neuron's output pathway for signals that it sends to other cells Neural communication: The Action Potential Action potentials play a central role in cell-to-cell communication: propagation of signals along a neuron's axon toward synaptic terminals situated at the ends of an axon these signals can then connect with other neurons at synapses or motor cells or glands **The brain:** Cerebrum: sensory perception, motor control, consciousness, learning, memory and many others Thalamus: role in memory, emotion, motor control, and sensation Hypothalamus: instinctive and automatic functions incl. water balance, blood pressure, metabolism, sleep, stress responses etc. Brainstem: sleep, automatic functions (e.g. breathing), consciousness Cerebellum: motor coordination **The endocrine system:** - The endocrine signals are hormones, like neurotransmitters for nervous system - Chemicals induce changes in other parts of the body - Slow, long-lasting response Major organs for endocrine system: - hypothalamus, pituitary & pineal glands - Thyroid and parathyroid glands - Thymus - Adrenal glands - Pancreas - Ovary, placenta - Testicle  Pituitary gland and hormones: - Anterior vs. posterior pituitary gland hormones Examples: - Growth hormone (GH): promotes tissue growth - Thyroid-stimulating hormone (TSH), or thyrotropin: stimulates the thyroid gland to secrete thyroid hormone, necessary for regulation of metabolism - Oxytocin (OT): the 'love hormone' (posterior one) Pancreas and its hormones: **The digestive system:** - The digestive system processes food, extracts nutrients from it, and eliminates the residue: - Ingestion: selective intake of food - Digestion: mechanical and chemical breakdown of food into a form usable by the body - Absorption: uptake of nutrient molecules into epithelial cells of digestive tract and then into blood or lymph - Compaction: absorption of water and consolidation of the indigestible residue into feces - Defecation: elimination of feces - Digestive system: the digestive tract and accessory organs - The digestive tract: a tube from mouth to anus (5m) à mouth, pharynx, esophagus, stomach, small intestine, large intestine - Gastrointestinal (GI) tract: stomach and intestines - Accessory organs: teeth, tongue, salivary glands, liver, gallbladder, and pancreas Saliva and salivary glands: - Saliva: watery solution of mucus, enzymes, and electrolytes à 1.0-1.5 L/day - It moistens the mouth, cleanses the teeth, inhibits bacterial growth, and dissolves molecules to stimulate taste buds - It lubricates food and binds particles together into a soft, slippery, easily swallowed mass - salivary amylase digests starch in food - major salivary glands Swallowing The stomach: - Food-storage organ, holds 1-4 L - It mechanically breaks down and liquefies the food and begins the chemical digestion of proteins and fat Small intestine: - digestion and nutrient absorption Large intestine: - Receives 500 mL/d of indigestible food residue à reduces it to 150 mL of feces by absorbing water and salts à eliminates the feces by defecation Education **The urinary system:** - Principal organs: two kidneys, two ureters, the urinary bladder, and the urethra Functions of kidneys: - filter blood plasma and excrete toxic metabolic wastes - regulate blood volume, pressure, osmolarity by regulating water output - regulate the electrolyte and acid-base balance of body fluids - secrete erythropoietin, stimulates production of red blood cells - final step in synthesizing calcitriol (vitamin D) - detoxify some drugs Urine formation: - Glomerular filtration rate (GFR) is the amount of filtrate formed per minute by the two kidneys combined - adult females: 105 mL/min or 150 L/day - adult males: 125 mL/min or 180 L/day - An average adult reabsorbs 99% of the filtrate and excretes 1 to 2 L of urine per day - valve at the opening of each ureter into the urinary bladder - contractions occur every few seconds to minutes that milk urine from the renal pelvis down to the bladder - The urethra conveys urine from the urinary bladder to the external urethral orifice - Parents produce gametes (sex cells) that meet andcombine genes in a zygote (fertilized egg) - Gametes' properties: motility to establish contact and nutrients for the embryo - Motility: sperm - Nutrients: egg (ovum) - The offspring receive genes from two parents Zygote - The organs that produce the gametes (testes of male and ovaries of female) are collectively called the gonads or primary sex organs - The other organs necessary for reproduction are called secondary sex organs, such as the penis, uterus, mammary glands - reproductive organs are also classified as external and internal genitalia The Male Reproductive System: - The testes (testicles) produce sex hormones and sperm, contained in the scrotum - The epididymis: site of sperm maturation and storage, contains a single coiled duct (6 m) embedded in connective tissue à It reabsorbs 90% of the fluid secreted by the testis - Sperm mature as they travel down the epididymis over a period of 20 days stored here and in ductus deferens The Female Reproductive System: - The ovaries are the female gonads, they produce egg cells (ova) and sex hormones - Each egg develops in its own bubblelike follicle and is released by ovulation, the bursting of the follicle **The Integumentary System:** integument = covering Skin: - two principal layers: a superficial epithelium, the epidermis and a deeper connective tissue layer, the dermis - Between skin and muscles a looser connective tissue layer, the hypodermis (epithelial tissue type) Functions: - Resistance to trauma and infection: epidermal cells are packed with keratin - Water retention: skin prevents the body from losing excess water - Vitamin D synthesis: Epidermal cells synthesize vit D needed for bone development and maintenance - Sensation: body's largest sense organ, equipped with a variety of nerve endings - Thermoregulation: increases or reduces blood flow close to the body surface and by sweating in response to overheating - Nonverbal communication: small facial muscles that act on the dermis to produce subtle and varied expressions - Accessory organs: hair, nails, glands - A hair is a slender filament of keratinized cells that grows from a hair follicle. Hair visible above the skin surface is called its shaft, below the surface, within the follicle, is the root with swelling end the bulb. Except near the bulb, all the hair tissue is dead! Nerve fibers called hair receptors coil around the follicle and respond to hair movements. - Nails: very thin dead cells, densely packed together and filled with parallel fibers of hard keratin. Serve as strong keratinized "tools" for digging, grooming, picking apart food. Nail plate, nail bed and nail fold. Nail matrix: growth zone beneath the skin. Fingernails grow at a rate of about 1 mm per week and toenails somewhat more slowly. - Cutaneous Glands: merocrine sweat glands, apocrine sweat glands, sebaceous glands, ceruminous glands, and mammary glands. - Merocrine sweat glands: widespread in the skin and produce watery perspiration that serves to cool the body