BIOL 4260 Human Evolu3onary Anatomy Lecture 12: Limb Development. Lecture 2: Fossil Record

Transcription

1 BIOL 4260 Human Evolu3onary Anatomy Lecture 12: Limb Development Lecture 2: Fossil Record

2 Outline Limb Evolution Limb Development Limb Function

3 A Few Definitions Appendicular skeleton girdles & limbs Pectoral girdle bony articulation of the upper limb with the axial skeleton Pelvic girdle - bony articulation of the lower limb Arm - upper aspect of upper limb (versus forearm) Leg - lower portion of the lower limb (versus thigh)

4 Pectoral Girdle

5 Pelvic Girdle

6 Forelimb & Hindlimb

7 ... first there were fins.. First jawed and finned fishes > 400 mya

8 Homologous upper limb structures derived from tetrapod

9 Die Bauplan HOX genes regulate shape and type of bones

10 Limbs Are Serial Homologues Proximal Distal

11 Limb Girdles Development in tetrapods allowed head mobility, independent movement of limbs Much larger in terrestrial animals - bear weight and provide attachment sites for muscles

12 Limb Development Limb buds Patterning of limb elements Patterning of limb musculature

13 Limb 4 weeks, C4 - 5 weeks, L1/2 - S3

14 Embryological Origins Outpocket of ectoderm and mesoderm Dermomyotomes: skin and hypaxial muscles Lateral plate mesoderm: bones Similar recipe for upper and lower limbs

15 Signaling molecules and gene expression 1. Upper limb outgrowth initiated by TBX5 & FGF10 2. Bone morphogenic proteins induce apical ectodermal ridge (AER), axes established 3. Fibroblast growth factors induce distal growth 4. More proximal areas slow division rates and differentiate

16 Pinky vs.thumb? ZPA - gene sonic hedgehog - regulates position of thumb- if misexpressed - creates mirror image

17 Limb Development Limb buds Patterning of limb elements Patterning of limb musculature

18 Budding Muscles Note:

19 Black - dorsal Grey - ventral Elevators Depressors

20 Transformation into tetrapod forelimb Basic organization remains Some dorsal muscles migrate onto back Some ventral muscles migrate onto chest

21 Transformation into mammalian forelimb Bring forelimb under body: 90 degree lateral rotation Dorsal muscles become caudal (posterior) Ventral muscles become cranial (anterior)

22 Limb moves under the body to improve locomotion Quadrupeds pronate forearm to locomote

23 Anatomical Position Forelimb: Pollex is lateral Developmentally ventral muscles - typically anterior Developmentally dorsal muscles - typically posterior

24 Innervation follows...

25 Developmentally Ventral Shoulder & arm: Pectoralis major Pectoralis minor Coracobrachialis Biceps brachii Brachialis Superficial forearm: Pronator teres Flexor carpi radialis Palmaris longus Flexor digitorum superficialis Flexor carpi ulnaris Deep forearm: Flexor digitorum profundus Flexor pollicis longus Pronator quadratus

26 Developmentally Dorsal Shoulder & arm: Supraspinatus Infraspinatus Subscapularis Latissimus dorsi Teres major Teres minor Deltoid Triceps brachii Anconeus Superficial forearm: Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Brachioradialis Deep forearm: Abductor pollicis longus Extensor pollicis longus Extensor pollicis brevis Extensor indicis Supinator

27 Lower Limb

28 Transformation into mammalian hindlimb Bring hindlimb under body: 90 degree medial rotation - opposite direction of forelimb Most dorsal muscles become cranial (anterior) Most ventral muscles become caudal (posterior)

29 Limb moves under the body to improve locomotion Quadruped foot is in correct position to locomote

30 Anatomical Position Hindlimb: Hallux is medial Developmentally ventral muscles - posterior and medial Developmentally dorsal muscles - anterior and lateral

31 Developmentally Ventral Pelvis and thigh: Gracilis pectineus Adductors (longus, brevis, magnus) Obturator externus Obturator internus Gemellii ms. Quadratus femoris Biceps femoris (Long) Semitendinosus Semimembranosus Posterior leg: Gastrocnemius Soleus Plantaris Popliteus Flexor digitorum longus Tibialis posterior Flexor hallucis longus

32 Developmentally Dorsal Pelvis & thigh: Psoas major Iliacus Tensor fasciae latae Gluteus minimus Anterior leg: Tibialis anterior Extensor hallucis longus Extensor digitorum longus Peroneus tertius Gluteus medius Piriformis Gluteus maximus Sartorius Lateral leg: Peroneus longus Peroneus brevis Quadriceps femoris Biceps femoris (short)

33 Limb Functions

34 Mammalian Limbs Limbs shifted from lateral position to below trunk - reduced pectoral girdle helps suspend thorax

35 Bipedalism Reinforcement of lower limb stability, strength Less demand on upper limb, reduction in weight, retained mobility

36 Limb Functions Mammals highly efficient - parasagittal movements Locomotion: Quadrupeds: walking, running, climbing, jumping, leaping, crawling, swimming, flying, gliding Bipeds: obligate walking and running Tool use: possible motivating force for human bipedalism - freeing of hands