Extended Lecture Outline
10.1 Urinary System
Excretion is the removal of metabolic wastes from the body. The kidneys are the primary organs of excretion.
Organs of the Urinary System
Kidneys
The kidneys are paired organs located near the small of the back, on either side of the vertebral column. The kidneys produce urine.
Ureters
The ureters conduct urine from the kidneys to the bladder. Peristaltic contractions cause urine to enter the bladder.
Urinary Bladder
The urinary bladder stores urine until it is expelled from the body through the urethra. The bladder wall is expandable.
Urethra
The urethra is a small tube that extends from the bladder to an external opening. The urethra has a different length in females than in males. In males, the urethra carries urine during urination and sperm during ejaculation.
Functions of the Urinary System
The functions of the urinary system include: excretion of metabolic wastes, notably nitrogenous wastes; maintenance of water-salt balance; maintenance of acid-base balance; and secretion of hormones.
10.2 Kidney Structure
Macroscopically, the kidneys are divided into the renal cortex, renal medulla, and renal pelvis. Microscopically, kidneys contain the nephrons.
Anatomy of a Nephron
Each nephron has its own blood supply; the afferent arteriole approaches the glomerular capsule and divides to become the glomerulus, a capillary tuft. The permeability of the glomerular capsule allows small molecules to enter the capsule from the glomerulus. The efferent arteriole leaves the capsule and immediately branches into the peritubular capillary network.
Parts of Nephron
Each region of the nephron is anatomically suited to its task in urine formation. The spaces between podocytes of the glomerular capsule allow small molecules to enter the capsule from the glomerulus, a capillary knot. The cuboidal epithelial cells of the proximal convoluted tubule have many mitochondria and microvilli to carry out active transport (following passive transport) from the tubule to blood. In contrast, the cuboidal epithelial cells of the distal convoluted tubule have numerous mitochondria but lack microvilli. They carry out active transport from the blood to the tubule.
10.3 Urine Formation
Glomerular Filtration
During glomerular filtration, small molecules including water, wastes, and nutrients move from the glomerulus to the inside of the glomerular capsule.
Tubular Reabsorption
During tubular reabsorption, primarily nutrients and water, moves from the proximal convoluted tubule into the blood of the peritubular capillary network. Only those molecules recognized by carrier molecules are actively reabsorbed. The amount of a substance that can be reabsorbed is limited by its number of carrier molecules.
Tubular Secretion
During tubular secretion, certain substances like hydrogen ions, creatinine, and penicillin move from the blood into the distal convoluted tubule.
10.4 Regulatory Functions of the Kidneys
The kidneys maintain the water-salt balance of the blood within normal limits. In this way they also maintain the blood volume and blood pressure.
Reabsorption of Water
Water is reabsorbed from the loop of the nephron and the collecting duct. This reabsorption of water requires reabsorption of salt and the establishment of a solute gradient dependent on salt and urea. Hormones regulate the reabsorption of sodium at the distal convoluted tubule and the reabsorption of water at the collecting duct.
Diuretics
Diuretics are chemicals that increase the flow of urine. Diuretics like alcohol and caffeine have various modes of action. Diuretic drugs can counteract high blood pressure.
Acid-Base Balance of Body Fluids
The normal pH for body fluids is about 7.4. If the blood pH rises above that, a person is said to have alkalosis. If the blood pH decreases below that, a person is said to have acidosis. These are abnormal conditions that need medical attention.
Acid-Base Buffer Systems
The pH of the blood stays near 7.4 because the blood is buffered. One of the most important buffers in the blood is a combination of carbonic acid and bicarbonate ions.
Respiratory Center
The respiratory center in the medulla oblongata increases the breathing rate if the hydrogen ion concentration of the blood rises.
The Kidneys
Only the kidneys can rid the body of a wide range of acid and basic substances. The kidneys are slower acting than the buffer systems and respiratory center, but they have a more powerful effect on pH.
10.5 Disorders with Kidney Function
Damage, especially recurring urinary infections, can lead to glomeruli that allow large molecules like proteins to be in the filtrate or glomeruli that simply do not function any more.
Hemodialysis
The usual form of hemodialysis involves cleansing the patient’s blood by passing it through dialysis tubing in contact with a dialysis solution. Wastes and excess salts pass out of the tubing into the dialysis solution. In continuous ambulatory peritoneal dialysis (CAPD), the dialysis solution is introduced into the peritoneal cavity. Wastes filter from the blood into the solution which is removed 4 to 8 hours later.
Replacing a Kidney
When kidneys fail, kidney transplants can be successful, especially if the donor is a close relative.
10.6 Homeostasis
The urinary system works with the other body systems to maintain homeostasis.
The Kidneys Excrete Waste Molecules
The kidneys remove metabolic waste which is absolutely necessary for maintaining homeostasis.
Water-Salt Balance
The kidneys regulate the water-salt balance which affects blood volume and blood pressure.
Acid-Base Balance of Blood
Only the kidneys can rid the body of a wide range of acidic and basic substances, so the kidneys have ultimate control over blood pH.
The Kidneys Assist Other Systems
The kidneys produce renin and assist the endocrine and cardiovascular systems.
Extended Lecture Outline
11.1 Overview of Skeletal System
The skeleton system consists of 206 bones (in adults) along with the cartilage and ligaments that occur at the joints.
Functions of the Skeleton
The skeleton supports the body, protects soft body parts, produces blood cells, stores minerals and fat, and permits flexible body movement along with the muscles.
Anatomy of a Long Bone
The shaft of a bone is called the diaphysis. It has a large medullary cavity whose walls are composed of compact bone. The expanded region at the end of a long bone is called an epiphysis. The epiphyses are composed largely of spongy bone that contains red bone marrow. A long bone is covered by the periosteum except for the articular cartilage on its ends.
Bone
Compact bone is made up of osteons, lacunae in concentric circles around a central canal. Canaliculi run through the matrix of bone, connecting lacunae and central canals. Spongy bone contains plates called trabeculae, the spaces of which are filled with red bone marrow for blood cell production. Bone cells are osteocytes.
Cartilage
Cartilage is weaker and more flexible than bone, and is slower to heal because of its lack of direct blood supply. Hyaline cartilage has a matrix made of collagen and is found at the ends of long bones and in the nose and trachea. Stronger fibrocartilage has thick rows of collagen fibers and is able to tolerate pressure and tension. Flexible elastic cartilage contains mostly elastin fibers and is found in the external ear and epiglottis.
Fibrous Connective Tissue
Fibrous connective tissue contains fibroblasts with collagenous fibers and makes up the ligaments that attach bone to bone and muscle to bone at joints.
11.2 Bone Growth, Remodeling, and Repair
Three different cell types are involved in bone growth and repair. Osteoblasts are bone-forming cells. Osteocytes are mature bone cells arising from osteoblasts. Osteoclasts resorb bone.
Bone Development and Growth
Ossification refers to the formation of bone.
Intramembranous Ossification
Intramembranous ossification occurs between flat sheets of connective tissue. Osteoblasts lay down bone, forming trabeculae. Compact bone is then laid down over the outside surfaces. Skull bones form this way.
Endochondral Ossification
Most bones form by endochondral ossification, with a cartilage model filled in with bone. Osteoblasts fill in areas of the center of the cartilage model that have begun to break down. Compact bone is also laid down under the periosteum. The epiphyses of long bones continue to grow from a growth plate.
Final Size of the Bones
When the epiphyseal plates close, bones can no longer increase in length.
Hormones Affect Bone Growth
Vitamin D and growth hormone (GH) affect the growth of the bones.
Bone Remodeling and Its Role in Homeostasis
In adults, the actions of osteoclasts and osteoblasts continually remodel bones. Bone recycling allows the body to regulate the amount of calcium in the blood. Bone remodeling also accounts for why bones can respond to stress.
Bone Repair
About 6 to 8 hours after a fracture, a hematoma (large blood clot) forms at the fracture site. A fibrocartilage callus fills in the break. A bony callus formed by osteoblasts replaces the cartilage and lasts for four months. Osteoclasts eventually remodel the bone, building a new medullary cavity. Fractures are named according to the type of break (e.g., spiral).
Vertebral Fusion
During fusion surgery, bone grafts are placed around the spine. The body joins the grafts to the vertebrae fusing the vertebrae together.
11.3 Bones of the Axial Skeleton
The axial skeleton lies in the midline of the body and consists of the skull, hyoid bone, vertebral column, ribs, and sternum.
The Skull
The skull is formed by the cranium and the facial bones.
The Cranium
The cranium is made up of eight bones that are incompletely fused in infants, leaving soft spots, or fontanels. Sinuses are found in the cranium. They reduce the weight of the skull and give resonance to the voice. The major bones of the cranium include the frontal bone, two parietal bones, an occipital bone housing the foramen magnum, two temporal bones, a sphenoid bone, and an ethmoid bone. The sphenoid bone makes up the floor of the cranium. The ethmoid bone helps form the orbits and the nasal septum.
The Facial Bones
The frontal bone of the skull forms the forehead of the face. The lower jaw is made up of the mandible. Zygomatic bones make up the cheekbones, and maxillae form the upper jaw. Two nasal bones form the bridge of the nose.
The Hyoid Bone
The hyoid bone is located superior to the larynx, anchors the tongue, and serves as a point of attachment for muscles used in swallowing.
The Vertebral Column
The vertebral column supports the head and trunk, protects the spinal cord and nerves, and is a site for muscle attachments. Each vertebra has facets that articulate with each other and spinous processes that project toward the back.
Types of Vertebrae
Cervical vertebrae are in the neck region and include the atlas and axis. Thoracic vertebrae are in the upper back and have an extra facet for rib attachment. Thick lumbar vertebrae are in the lower back. Five sacral vertebrae fuse to form a sacrum. The coccyx, or tailbone, is at the base of the vertebral column.
Intervertebral Disks
Intervertebral disks, formed of fibrocartilage, provide padding between vertebrae.
The Rib Cage
The rib cage is composed of the thoracic vertebrae, the ribs and their cartilages, and the sternum.
The Ribs
The 12 pairs of ribs all connect to the thoracic vertebrae. The upper seven pairs of ribs connect to the sternum via costal cartilage. The lower two pairs of ribs are “floating ribs” because they are not attached to the sternum.
The Sternum
The sternum (breastbone) protects the heart and lungs. It is made of the manubrium, the body, and the xiphoid process.
11.4 Bones of the Appendicular Skeleton
The appendicular skeleton is made up of the pectoral and pelvic girdles, and the arm and leg bones.
The Pectoral Girdle and Upper Limb
The pectoral girdle consists of the scapula (shoulder blade), and the clavicle (collarbone). The glenoid cavity articulates with the head of the humerus. The humerus is the bone of the upper arm. The radius and ulna make up the lower arm. The hand is made up of eight carpal bones, with five metacarpals and the phalanges of the fingers and thumb.
The Pelvic Girdle and Lower Limb
The pelvic girdle consists of two heavy coxal bones, fused at the sacrum. Each coxal bone is made up of the ilium, ischium, and pubis, all fused at the acetabulum. The male pelvis and the female pelvis differ somewhat due to different functions. The female pelvis is more flared. The thigh contains the femur, and the lower leg is made up of the tibia and fibula. The ankle contains seven tarsal bones, and five metatarsals make up the arching instep of the foot.
11.5 Articulations
Bones are joined at the joints, which are classified as fibrous, cartilaginous, or synovial. Fibrous joints are immovable. Cartilaginous joints are connected by hyaline cartilage and tend to be slightly movable. Synovial joints are freely movable.
Movements Permitted by Synovial Joints
Synovial joint movements include flexion, extension, abduction, rotation, circumduction, inversion and eversion.
Extended Lecture Outline
12.1 Overview of Muscular System
All muscles contract or shorten.
Types of Muscles
Smooth muscle fibers are spindle-shaped cells, each with a single nucleus. Contraction of smooth muscle is involuntary. Cardiac muscle forms the heart wall. Its fibers are generally uninucleated, striated, tubular, and branched. Cardiac fibers relax completely between contractions, which prevents fatigue. Skeletal muscles fibers are tubular, multinucleated, and striated. Skeletal muscle contraction is voluntary.
Functions of Skeletal Muscles
Skeletal muscles support the body, make bones move, help maintain a constant body temperature, assist movement in cardiovascular and lymphatic vessels and help protect internal organs and stabilize joints.
Skeletal Muscles of the Body
Skeletal muscles are attached to the skeleton, and their contraction causes the movement of bones at a joint.
Basic Structure of Skeletal Muscles
A whole muscle contains bundles of skeletal muscle fibers called fascicles. Within a fascicle, each fiber is surrounded by connective tissue, and the fascicle itself is also surrounded by connective tissue. Muscles are covered with fascia, a type of connective tissue that extends beyond the muscle and becomes its tendon, anchoring the muscle to the bone.