Anatomy Lecture 2: Tissues and Structures of the Body PDF

Anatomy lecture 2: Tissues and structures of the body  Outline Tissues & structures of the lower limbs A bit of radiology Summary Look forward to next week  The organisation of body components Chemicals – “Cell bits” (organelles and so forth) Cells Tissues...

Anatomy lecture 2: Tissues and structures of the body  Outline Tissues & structures of the lower limbs A bit of radiology Summary Look forward to next week  The organisation of body components Chemicals – “Cell bits” (organelles and so forth) Cells Tissues Organs Organ systems A whole body  What structures are there in the body? Bones (Joints) Cartilage Fascia / Adipose Ligaments tissue Synovium/Bursa Vascular Muscles structures Tendons / Neural structures aponeurosis Skin  Types of tissue Histology is the study of tissues Broadly 4 types of tissue: – Epithelial: A covering material – Connective: Connects things and provides support. – Muscle: Contracts to cause or control motion – Nervous: Provides communication between body parts by transmission of electrical impulses  Structures and tissue type Structures within the body may be made of one type of tissue or many types. – Bone is pretty much connective tissue. – The heart has epithelial tissue, muscle and connective tissue, it also has nerves within it.  Bone A living, continuously changing structure that remodels itself in response to the stresses placed on it: Wolf’s Law Functions – Protection – Framework for other structures – Acts as a system of levers and pulleys to provide motion – Reservoir for calcium and fat – Formation of blood cells  Bone: structure Cells: Osteocytes – Osteoblasts lay down new bone – Osteoclasts ‘eat’ old bone Matrix, dense, tough connective tissue lattice, filled in with Calcium phosphate; resilient, very slightly elastic and resists compression. Supplied by vascular structures and nerves. Surrounded by periosteum – 2 layers: outer one, very fibrous; inner one is highly vascular, ‘cambium’, layer containing progenitor cells.  Classifications of bone Compact (cortical) – Strong, dense, forms tubular bodies, filled with marrow Cancellous (spongy) – Lattice of bony spicules, trabeculae, (looks like the inside of a crunchy). – Helps redistribute stress and shock absorb Both forms appear in different types of bone but the proportion varies depending of job that the bone does. Compact bone: structure Cancellous bone: structure The tibia  Bone classifications Based on shape or region – Long bones Compact (cortical) shaft, cancellous ends, ends form joint, covered with hyaline cartilage. – E.g. Femur, tibia, metatarsal – Short bones Mainly cancellous surrounded by a compact shell, more cube shaped. Joint surfaces covered in hyaline cartilage Often found in the foot: calcaneus, talus  Bone classifications Flat bones – Thin inner and outer layer of cortical bone separated by a layer of cancellous bone. E.g. Skull, scapula Irregular bones – Thin shell of compact bone surrounding cancellous bone. – Tend to be an odd shape E.g. vertebrae of the spine  Bone classifications Sesamoids – Are they true bones or bony nodules? – Exist within the tendons of muscles where the tendon would otherwise rub over a bony prominence. Patella (knee cap) Sesamoid bones in FHB under big toe joint  Bone classifications Vertebrae - irregular Talus - short Femur - long Scapula - flat Big toe joint - sesamoids  Bone marrow Occupies the cavities in long and short bones and the gaps between trabeculae in other cancellous bones. In children it is all red, haematopoetic – Red & white blood cells, platelets Gradually replaced after the age of about 7 by yellow marrow, fatty. – Some white blood cells About 50% of each by adulthood.  Bone development Two methods of formation – Membranous Bone develops directly from a connective tissue membrane. Less common. – Endochondral Cartilage model laid down, gradually replaced by bone formation This is how limbs form May take 20+ years Different bones ossify at varying rates Endochondral bone development  Ossification rates Calcaneus. At birth Talus. At birth 12 - 20 years Navicular. Cuboid. At birth 3 years Medial cuneiform. Intermediate 2 years cuneiform. 2 1/2 yr 1st metatarsal. Lateral At birth cuneiform. 3 - 14 - 21 years 6 months 2nd - 5th Also: metatarsals. At birth Tibia. 6 months Phalanges. 16 - 18 years At birth Fibula. 1 year 18 years 16 - 18 years Radiographic view of adult and child knees  Bones of the pelvis Sacrum Ilium Anterior, superior, iliac crest iliac spine Anterior, Sacroiliac joint. inferior, iliac spine Hip joint Pubis Obturator foramen Femur Ischium Pubic symphysis  The knee Femoral condyles Femur Patella  Rear foot & ankle Fibula Tibia Talus  Cartilage Is a form of connective tissue Cells and fibres of collagen embedded in a gel like matrix 3 types: – Hyaline. Important in formation of bone, covers the ends of bones to provides protection, lubrication. – Fibrocartilage. Lots of fibres in small amount of matrix. Tough, may be found in different joint types doing a variety of jobs.  Cartilage Elastic cartilage. Elastic fibres embedded in matrix. Springy. Visible in the external part of the ear. Hyaline and fibrous cartilage may calcify and turn to bone over time. Cartilage is aneural & avascular, can’t repair itself very well.  Cartilage Elastic cartilage - forms the Hyaline cartilage - covers bone ends external part of the ear, the Fibrous cartilage - forms menisci of knee pinna  Ligaments A band or cord of connective tissue linking 2 or more structures. Often but not exclusively, link a bone to another bone, to form a joint. – E.g. around ankle, knee, hip – This type of ligament will allow movement in one direction but restrict it in others. E.g. ankle  Ligaments Two classifications of ligament – Inelastic Dense, tough bundles of collagen fibres in a matrix. – E.g. ankle & knee – Elastic Elastic fibres in a matrix – Plantar calcaneonavicular ‘spring’ ligament in the foot. Also: ligaments within the capsule that surrounds a joint are called intracapsular ligaments, those outside are called extracapsular.  Ligaments Intracapsular Extracapsular  Synovial membranes / sheathes and bursae All of the above are sacks full of fluid but they do somewhat different jobs. – Synovial membranes are the inner surface of the capsule that surrounds a moveable joint. It secretes fluid to help lubricate the joint. The outside of the membrane is continuous with the periosteum that surrounds the bones and helps hold the joint together. Synovial membrane  Synovial sheathes Similar in structure to a synovial membrane round a joint but sheathes surround tendons, where the tendon: – Moves a lot – Goes round a bend – Pass under or through other structures Their job is to reduce friction and protect the tendon Synovial sheathes  Bursae Again a bursa is a fluid filled sack but this time it’s job is to sit under a tendon in order to separate the tendon from a bone where the tendon passes over a bony lump. The bursa prevents rubbing and irritation of the tendon. Unfortunately sometimes bursae can themselves become inflamed and painful! Bursa  Muscles Muscles are the structures by which movements of or within the body are created or controlled. Three types of muscle – Cardiac, found in the heart. – Smooth, found in internal organs such as blood vessels and the gut. – Skeletal, this is the sort we’re most concerned with in this module  Skeletal muscle Under conscious control of the brain Fibres are striated (stripey) Muscles work by contracting (true of all muscles not just skeletal) Lots of different types of contraction though  Skeletal muscle All have a point of origin, that doesn’t move much, usually but not always a bony attachment. All have a muscle belly where the bulk of the muscles fibres are, fibres of the belly slide over each other in contraction so the muscle becomes shorter and fatter. All have a point of insertion via a tendon or sometimes an aponeurosis which moves more than the origin, again it is usually but not always a bony attachment. The tendon usually crosses a joint, causing motion around the joint Muscle structure  Skeletal muscle types Type 1 – Slow twitch, red (myoglobin) Marathon runner Type 2a – Quite fast twitch, white 800m runner Type 2x (used to be called 2b) – Fast twitch, white 100m runner, powerlifter A few lucky people may have what’s now called type 2b, which are ultra fast fibres (Colin Jackson?)  Muscles & stress Muscles and other soft tissues respond to stress and become stronger. If you run long distances you become better adapted to endurance. If you lift heavy weights you become more powerful. By the same token if you don’t use it you lose it. Davis’s law. Muscle shapes  Types of muscle contraction Dynamic Static Concentric Eccentric Isometric Force generated Force generated towards the towards the centre of the centre of the muscle, muscles muscle but the shortens, muscle is movement lengthening, Force generated occurs. steadily under towards the centre of conscious control. the muscle but no Used to control motion occurs. Useful motion. in stabilising a body part, e.g. deep abdominal muscles in gait. Both may be considered isotonic (equal force) or isokinetic (equal speed).  Jobs that muscles do Prime mover (agonist) – Chief muscle or group that causes a movement. E.g. quadriceps extend the knee Antagonist – Skeletal muscles work via antagonistic pairs, one muscle or group cause or control motion one way the antagonists do it in the opposite direction. E.g. the hamstrings antagonise the quadriceps – Reciprocal inhibition  Jobs that muscles do Fixator (stabiliser) – Muscle contracts isometrically to stabilise the origin. No movement occurs but a body part is fixed in position. E.g. gluteal muscles when standing on one leg or deep abdominal muscles. Synergist – A muscle that assists another muscle to increase the amount of ‘pull’ or alter the direction of pull. It may stabilise an area so a prime mover can work more efficiently, E.g. flexor accessorius in the foot  Remember! Skeletal muscle is under the conscious control of the brain. In order for this to happen there is a very complex network of sensors / receptors that measure: – Pressure, temperature, force, position, movement, pain etc. etc. etc. This information is sent to the brain, via the afferent nervous system, where it is processed and the brain tells the muscles what to do next via the motor nerves.  Tendon / aponeurosis Muscles are attatched to bones (usually) via tendons and sometimes by an aponeurosis. These are both formed by strands of fibrous tissues from the ends of the muscles and the membrane that surrounds the muscles (fascia).  Tendon / aponeurosis Tendons are long inelastic cords of connective tissue, – E.g. Extensor hallucis longus. Tendons cross over joints and may cause motion some distance from the muscle, they can also go round corners. Aponeurosis is a very thin but wide sheet of tissue, – E.g. Ventral abdominal aponeurosis Aponeurosis more likely to be used to stabilise an area. Tendon / aponeurosis Extensor hallucis longus Ventral abdominal aponeurosis  Joints A joint is where two (or more) bones come together. There may or may not be movement there. Types of joint: – Fibrous joints (sutures, syndesmosis), Negligible or no movement – Cartilaginous joints (synchondrosis, symphysis) Small amount of movement – Synovial joints Large range of motion  Fibrous joints Margins of the bones overlap and interlock irregularly like the pieces of a jigsaw. Inherently rigid & stable. Sharpey’s fibres bind the bones to hold them together very firmly. – E.g. the sutures that hold the separate bones of the skull together.  Fibrous joints OR – Bones fit very closely together with their respective shapes leaving little or no gap. – Joint is then linked & surrounded by very tough connective tissue. E.g. inferior tibiofibular syndesmosis  Cartilaginous joints Two sorts: – Primary: two bones or parts of bones separated by strip of hyaline cartilage. – Secondary: Bones are united by a plate of fibrous cartilage and the bone ends have a thin strip of hyaline cartilage. E.g. symphysis pubis  Synovial joints Highly moveable. Contain all of the things we’ve spoken about today. Some just move in one direction other move simultaneously in many directions. Often, trade off between stability and maneuverability. Depends on: – Joint shape – Ligament strength – Muscle control Joint shapes  Synovial joint shapes Hinge – Extension and flexion of a body segment. – E.g. Ankle or elbow  Synovial joint shapes Ball & socket – Ball shaped head of a bone fits into a bowl shaped socket. – Allows free movement in any direction or combination. – E.g. Hip, shoulder  Synovial joint shapes Plane – Almost flat surfaces of the bones glide over each other. – E.g. Some of the tarsal bones of the foot  Synovial joint shapes Saddle joints – Opposite shaped ‘saddles’ allow up and down plus side to side motion but not rotation. – E.g. Joint at the base of the thumb.  Synovial joint shapes Ellipsoid – Like a ball & socket but less range of motion than a true b&s. – E.g wrist  Synovial joint shapes Condyloid – Two convex & two concave surfaces. – Mainly flexion and extension, some side to side, a little rotation. – E.g. base of the toes and between toes bones, knee..  Synovial joint shapes Pivot – Central bony pivot surrounded by a bony ligamentous ring. – Rotation is the only motion possible. – E.g. atlantoaxial joint in the neck  Fascia Membranes that surround the deep structures within the body. Looks a bit like clingfilm. Two types: – Superficial Surrounds everything under the skin, holding it together. – Deep Divides the deep structures into compartments within a body segment.  Superficial fascia Mixture of loose, areolar connective tissue and adipose tissue (fat). Joins the dermis of the skin to the underlying deep fascia. May be adaptations of it with collagen fibres binding the skin firmly to the deeper structures. Also, the fat deposits may be organised with fibrous tissue to provide extra padding.  Deep fascia Membranous layer of connective tissue that surrounds muscles and groups of muscles dividing them into clearly defined compartments. Handy for us, as muscles within a compartment tend to be supplied by a common nerve and set of vascular structures. – E.g. Thigh compartments. Fascial compartments  Deep fascia May be adaptations of the deep fascia: – Thickenings of the fascia, in order to assist other structures. Retinacula: Holds tendons, blood vessels, nerves in place where they go round a corner. OR Tracts, such as the iliotibial tract which assist with stability of the lateral thigh / knee. Plantar fascia?  Fascial adaptations Extensor retinacula of the foot /ankle Iliotibial tract  Cardiovascular system Heart and blood vessels pump blood around the body & back to the heart 2 systems: – Pulmonary. Lungs – Systemic. Everywhere else Heart is basically a fluid pump Muscular bag with 4 chambers, as the muscle contracts it pushes the blood to other places in the body.  Other vascular structures Take blood and other fluid to and from the heart. – Arteries – Arterioles – Metarterioles – Pre-capillary sphincters – Capillaries – Venules – Veins – Don’t forget lymphatics  What does the CV system do? Exchange of gases: oxygen in, carbon dioxide out. Also: – Delivers nutrients & hormones – Removes waste products Protection: – Clotting, leucocytes, antibodies etc. Temperature regulation Assists with homeostasis  Arteries Muscular, elastic walls deliver blood from the heart to other places. Aids heart pumping High pressure system  Veins Less muscular and elastic than arteries. Deliver blood back to the heart from everywhere else. Lower pressure system than arteries (generally). Have one way valves, in order to prevent back flow. Artery & vein structure  Capillaries Once the blood has got to where it’s going, it passes through pre-capillary sphincters (valves) into capillaries. Capillaries are tiny and have walls only 1 cell thick, there are many, many miles of them though. They are very leaky. Oxygen, nutrients etc. leak out; Carbon dioxide and waste products leak in and are carried away.  Anastomosis Joining up of vessels Allows blood to pass from one vessel to another, useful if a vessel becomes blocked. Can join: – Arteries to other arteries – Veins to other veins – A combination of the above Putting it all together  Lymphatics Work in parallel with the veins to take fluid & proteins away from tissues and back into the blood. Drain into large veins Also, have protective function, lymph nodes act as a filter inhabited by phagocytes / antibodies. Lymphatics  The nervous system The body’s way of working out what’s going on and telling itself what to do next. Can be classified in a number of ways: – Central NS Brain & spinal cord – Peripheral NS Everything else Also: – Sensory vs motor – Somatic vs autonomic – Sympathetic vs parasympathetic  Organisation of the nervous system CNS Impulses Brain & spinal cord, Integration & control to brain Impulses PNS from brain Cranial & spinal nerves Communication between brain and everywhere else Somatic Autonomic Afferent & efferent Unconscious control of body functions Sensory Motor Sympathetic Parasympathetic  Somatic: Afferent & efferent Afferent (sensory) – Pain, temperature, vibration, pressure, muscle and tendon tension, joint position, etc. Efferent (motor) – In response to information received from the above instructions sent to muscles in relevant body parts about how to move next.  Autonomic Generally speaking: – Sympathetic system revs things up, ready for action. – Parasympathetic slows things down, in order to rest and recover. – BUT all of the above happens ALL of the time, it’s just a question of the relative proportion of each. Cranial nerves Spinal nerves  Neurons Neural tissue exits the brain & passes down the central hole in the middle of the vertebrae. The nerves then exit out from the spinal cord sideways and travel to the rest of the body. A nerve is a bundle of individual neurons. Electrical impulses in an individual neuron tend to only travel in one direction. Structure of a neuron  Nerve roots The nerves that supply the body exit the spinal column in predictable places. The ones that supply the lower limbs exit in the lumbar and sacral regions of the spine. – E.g. we know that the nerves that supply the heel exit the spine at S1.  Lumbar & sacral plexi Lumbar plexus – L1 - L5 Sacral plexus S3 S4 – L4 - S5  Main nerves of the lower limbs Femoral – L2 - L4 Obturator – L2 - L4 Sciatic – L4 - S3  Skin Largest organ in the body. Otherwise known as the integument Covers about 1.5 - 2 sq m Weighs about 16% of body weight Basically: – It keeps the outside out & – Your insides in But the reality is a bit more complex than that  Functions of skin Major functions – Protection from: physical attack, chemicals, bacteria, dehydration, the sun etc. – Temperature control – Site for receptors. – Synthesis of vitamin D – Communication  Structure Layers – Dermis Deeper, contains: – Blood vessels – Nerves / receptors – Hair roots – Glands Connected to deeper structures via superficial fascia – Epidermis Skin surface Stratified (layered) Palms and soles thicker & hairless Structure  Summary Introduced basic anatomical concepts Various tissues and structures How they relate to each other After you have read through the notes & digested the information, you should be able to name them and state what each of them do. LOTS OF IT, ISN’T THERE!  Next week Read through these notes and an anatomy text book on the issues we’ve covered today, to consolidate today’s information. Consider surface anatomy as directed. Prepare for osteology of lower limb Look at anterior compartment of thigh Monday 8.45 prompt from senate 8.55ish from Park and ride.